From 714b8ae84d7379d71310e513ff9ebf42644b8ed5 Mon Sep 17 00:00:00 2001
From: cvs
+DIFRAC Manual for TRICS
+
+
+ A Fortran 77 Control Routine for 4 Circle
+ Diffractometers
+
+ by
+
+ E. J. Gabe, P. S. White and G. D. Enright
+
+ Steacie Institute for Molecular Structure
+ National Research Council of Canada
+ Ottawa, Ontario, Canada
+
+ and
+
+ Department of Chemistry
+ University of North Carolina
+ Chapel Hill, North Carolina, U.S.A
+
+
+ Adapted for TRICS at SINQ, PSI by
+
+ Mark Koennecke
+ Laboratory for Neutron Scattering
+ Paul Scherrer Institute
+ CH-5232 Villigen-PSI
+ Switzerland
+
+
+
+
+
+ DIFRAC performs all the fundamental operations associated +with an X ray diffractometer for crystal orientation and +intensity measurement. + + The basic aims behind DIFRAC are : + + 1. to provide a comprehensive set of crystallographic functions +which can be used with any diffractometer controlled by a PC; + 2. to provide a user interface which is easy to learn; + 3. to make the program easily portable for different + instruments. + + These aims, particularly the last, have to a large extent +dictated the structure of the program which is highly modular and +uses many of the portability concepts developed for the NRCVAX +structure system. + + The first aim has been realized via a large set of +subroutines providing functions which are common to all +diffractometers. These are written in F77 and constitute by far +the largest part of the code. The program runs on a PC under +MS DOS using Microsoft compilers. All calculations are carried +out in a standard right handed Euler axial system following the +definitions used in Busing W.R. and Levy H.A., Acta Cryst., +(1967), 22, 457. The facilities available provide the user with +a comprehensive set of basic functions for examining crystals, as +well as more powerful functions which make extensive use of +symmetry for orientation and intensity measurement. + + The second aim was originally achieved with a 2 letter +mnemonic command structure and a simple windows type of screen +presentation. A later version will use a fully windowed +interface. + + The third aim is achieved by isolating any modifications +required to drive different instruments to a small set of +subroutines in F77, C or assembler, which actually address the +interface. In this way changes to drive different instruments, +e.g. to drive a Kappa geometry machine, need only be made in +these routines, while the bulk of the code remains constant. + + The program uses a single binary file to hold all relevant +crystal information and intensity data. This is a direct access +file usually called IDATA.DA. If this file does not exist when +the program is started it is created and default values are +assigned to all parameters. If the file does exist when the +program is started, existing values from the file are used. +During data collection each reflection is written to the file as +soon as it is measured so that in the case of a crash no data is +lost. If the need arises, the file is automatically lengthened to +accomodate more data. A routine is available for reading and +translating the binary IDATA.DA file into ASCII, or it can be +read directly by the NRCVAX package. + + The emphasis has always been on giving the user a reasonably +comprehensive, but simple method to make the instrument perform +the sorts of operations which facilitate initial examination, +alignment and intensity measurement for randomly oriented +crystals. Commands like CR, IM, LP allow the easy manipulation +of a reflection which is already in the detector. Others like +AL, IR, IE, IP align or measure reflections from a list. An +important difference between this routine and some other control +routines is that the list is transparent to the user. The +commands set up the list as well as performing the operation. +There are no list manipulation commands as such, though the list +can be editted from within a command. This makes for a more +comfortable and direct feel to running the program. + + A second distinction between DIFRAC and other such routines, +is the extensive use of symmetry information. The routine can +interpret space group symbols, and use the symmetry matrices +generated to measure or align equivalent reflections. The +routine also uses symmetry to decide on the unique part of +reciprocal space to measure, which means that no redundant +reflections need be measured. If further data is needed, the +routine will automatically continue to measure symmetry +equivalent data sets until the whole sphere, within the q limits, +is collected or until stopped by the user. + + A further difference is the continuous display of reflection +profiles. This is an invaluable help in deciding whether the +crystal is suitable for analysis, and for monitoring the +measurement process. It is not usually realized how useful this +can be during intensity measurement, both as a security blanket +and as a diagnostic. It always allows a user 'to get a better +feel' for the crystal under investigation and quite often shows +crystal or misalignment problems that the user would otherwise be +unaware of, but which with corrective action, will ultimately +improve the quality of the data. + + Adaptions for TRICS + + The DIFRAC system has been included into the SICS instrument +control software. This manual has been derived from the original +DIFRAC manual by removing all redundant commands. The DIFRAC +subsystem in SICS is accessed by prepending each DIFRAC command +with the string dif. Please note, that SICS cannot be interrupted +when it is waiting for command input for DIFRAC. Also at least +two characters of input are required in the SICS command line +client in order to handle a platform dependency bug in Java. + ++ + +
+
+ The following is a concise list of the 2 letter commands +available with a one line description of each. This is meant +only as a quick reference to the commands and a reference to the +manual page with the full description is given. The program has +been developed over many years and the whole routine has +gradually been made more automatic. As a result some of the +earlier commands are probably redundant. + + The commands are in alphabetical order in groups with +roughly related function. A list in the rough order of use to +setup and measure a crystal is given after the alphabetic list. +If no command or an invalid command is given at the command +prompt, various help menus are suggested. + + Group A: Terminal Data Input Commands + + +BD all Basic Data (includes CZ DH FR LA OM OR PS RR SD SE TM TP) +CZ Correct angle Zero values ... ... ... ... ... +FR First Reflection to be measured ... ... ... ... +LA LAmbda for the wavelength in use, usually a1 ... ... +OM Orientation Matrix ... ... ... ... ... ... +PS PSi rotation data ... ... ... ... ... ... +RO Re Orientation reflections: frequency and h, k, ls ... +RR Reference Reflections: frequency and h, k, ls ... ... +SD Scan Data: measurement type, width, speed, profile control +SE Systematic Extinctions ... ... ... ... ... +SG Space Group symbol ... ... ... ... ... +TM 2q Min and max values ... ... ... ... ... +TP Time and Precision parameters for intensity measurement ... + + + Group B: Crystal Alignment Commands + +AL ALign reflections and their symmetry equivalents for MM ... +AR Align Resumption after interruption ... ... ... ... +A8 Align the 8 alternate settings of reflection for angle zeroes +CH CHoose reflections from the PK list for use with M2 or M3 ... +CR Centre the Reflection which is already in the detector ... +LC 2q Least squares Cell with symmetry constrained cell ... +MM Matrix from Many reflections by least squares on AL data ... +M2 Matrix from 2 indexed reflections and a unit cell ... ... +M3 Matrix from 3 indexed reflections ... ... ... ... +OC Orient a Crystal, i.e. index the peaks from PK ... ... +PK PeaK search in 2q, c, f for use with OC ... ... ... +RC Reduce a unit Cell ... ... ... ... ... ... +RP Rotate f 360, centre and save any peaks found ... ... +RS ReSet the cell and matrix with the results from RC ... ... + + + Group C: Intensity Data Collection + +GO Start of intensity data collection ... ... ... ... +K Kill operation at the end of the current reflection ... +Q Quit after the next set of reference reflections ... ... +LR Last Reflection written to IDATA.DA ... ... ... ... + + + Group D: Angle Setting and Intensity Measurement + +GS Grid Search measurement in 2q, w or c ... ... +IE Intensity measurement for Equivalent reflections ... ... +IM Intensity Measurement of the reflection in the detector ... +IP Intensity measurement in y steps for empirical absorption +IR Intensity measurement for specified Reflections ... ... +LP Line Profile plot on the printer ... ... ... ... +SA Set All angles to specified values ... ... ... ... +SC Set c to the specified value ... ... ... ... +SO Set w to the specified value ... ... ... ... +SP Set f to the specified value ... ... ... ... +SR Set Reflection: h,k,l,psi. ... ... ... ... ... +ST Set 2q to the specified value ... ... ... ... +TC Timed Counts ... ... ... ... ... ... +ZE ZEro the instrument Angles ... ... ... ... ... + + + Group E: Photograph Setup Commands + +PL Photograph in the Laue mode ... ... ... ... ... +PO Photograph in the Oscillation mode (same as OS) ... ... +PR Photograph in the Rotation mode ... ... ... ... + + + Group F: General System Commands + +AH Angles to H,k,l (same as IX) ... ... ... ... ... +AI Ascii Intensity data file conversion ... ... ... +AP Ascii Profile data file conversion ... ... ... ... +BC Big c search for y rotation ... ... ... ... +BI Big Intensity search in the IDATA.DA file ... ... ... +HA H,k,l to Angles (same as RA) ... ... ... ... ... +IN INitialize integer parts of angles ... ... ... ... +NR set the NRc progam flag ... ... ... ... ... +P9 rotate f by 90ø ... ... ... ... ... F3 +PA Print Angle settings ... ... ... ... ... +PD Print Data of all forms ... ... ... ... ... +RB Read the Basic data from the IDATA.DA file ... ... ... +SW SWitch register flags setting ... ... ... ... +UM (UMpty) Count unique reflections within 2q limits ... ... +VM set the circles to the View Microscope position ... ... +WB Write the Basic data to the IDATA.DA file ... ... ... ++ +
+
+ This section contains a list of operations with the +applicable commands to setup, measure intensities and get an +accurate cell for an unknown crystal. It is meant only as a +guide to first time users and should not be taken as hard and +fast. + + Crystal Setup + + 1. Mount the crystal and optically centre it on the instrument + with VM. + 2. Use PD to see what values have been assigned to the basic + parameters. + Change the wavelength if necessary with LA and 2q limits + with TM. + 3. Find and centre 10 to 15 peaks with PK. + 4. Index the peaks with OC, which will automatically progress + to RC and RS if necessary. + 5. Find reflections with somewhat higher angles with IR, and + centre them with AL using Friedel equivalents. + 6. Calculate a better matrix with MM. + 7. Save the orientation matrix with WB. + + + Data collection setup + + 8. Ensure that the scan data and time parameters are reasonable + and reset them if necessary with SD and TP. + 9. Find medium strong reflections which are well distributed in + reciprocal space with IR, to be used as reference or + standard reflections. Enter them with RR. +10. Adjust the scan data with SD after seeing the profiles from + step 9 and set the detector slits. +11. Find re orientation reflections with IR. Enter them, or + ensure that re orientation is not done, with RO. +12. Enter the Laue group symbol with SG. Use the lower symmetry + group if there is an ambiguity, e.g. 4/m and not 4/m m m. +13. Try to pin down the Laue group and possibly the space group + as well with IE. Enter the corrected group with SG. +14. Make adjustments to any of the basic parameters (PS, SD, TM, + TP etc) if necessary. +15. Issue the GO command and answer the questions to start + data collection. +16. Stop the measurement with K or Q when sufficient data have + been collected. + + + Accurate cell setup + +17. Search the unique data on the IDATA file with BI for the 25 + strongest reflections with 2q greater than a minimum. +18. Narrow the detector slits and enter about 50 reflections + (including symmetry and Friedel equivalents) for AL, which + will then centre them. +19. Maybe use A8 to get instrument zeroes and enter them with + CZ. This procedure could also be used before step 6. +20. Get an accurate cell and esds with MM on AL results. +21. Possibly use LC on the 2q data alone. ++ + +
+
+ Normally the program uses 4 files which are called IDATA.DA, +ORIENT.DA, goniom.ini and LPT1. IDATA.DA is the most important +and ORIENT.DA is used only as a scratch file during crystal +orientation. goniom.ini is the instrument initialization file. +LPT1 will contain all output which is directed to an attached +printer, if there is no printer present. + + The IDATA.DA file is a binary direct access file with +records of 85 4 byte variables. The contents of these records is +as follows : + + Records Contents + 1 to 3 All the basic data for the machine and crystal. This +is the data + which is written by WB and read by RB. + 4 to 8 Symmetry information generated by the SG command. + 9 Information for an automatic restart after +data collection has been + interrupted. +10 Space group symbol. +11 to 15 Not used at present. +16 to 19 List of h,k,ls for use with AL. +20 to N Intensity data stored 10 reflections per record. + + If the IDATA file does not exist when the program is started +it is created with a length of 700 records which will hold 6800 +reflections. This should be adequate for most data collections, +but the file will be extended by 100 records at a time as needed. +As the file always exists before it is used there is no data loss +in the event of a crash. However, as the same file is always +used for data collection it is necessary to copy or rename it +before another collection is started, or the data will be +overwritten. + + When the file is created the program assigns default values +to all essential parameters in records 1, 2 and 3. Defaults are + +Cell dimensions 10.0, 10.0, 10.0, 90.0, 90.0, 90.0 +Wavelength 0.70932 (MoKa1) +2q min max 2.0, 100.0 +h,k,l max 22, 22, 22 +Angle zeroes 0.0, 0.0, 0.0 (2q, w, c) +Orientation matrix 0.1 0.0 0.0 + 0.0 0.1 0.0 + 0.0 0.0 0.1 + This corresponds to the cell above with axes +along the + X, Y, Z instrument axes. +Scan data As 1.0, Bs 0.7, Cs 1.0 + for a scan width of As + Bs*tan(q) + Cs, + w/2q scan with profile analysis; speed +4.0/minute. +Background time 0.1 of scan time +Systematic absences None +Reference reflection 4, 0, 0 taken every 100 normal reflections +Psi rotation None +Reorientation data None +Reflection sequence As for +h, +k, +l orthorhombic data with l +varying fastest + and h slowest. + + If the IDATA file exists when the program is started, then +the values on the file are used until changed. The form of the +intensity data in records 20 upwards is shown under the GO +command. + + The file ORIENT.DA is also a binary direct access file with +records of 85 4 byte variables. This file holds the data and +results of all orientation operations, and need never be kept, +though it is retained on exit from the program. + + The file goniom.ini contains data to initialize the program +when it is started. The file is in plain ASCII form and heavily +commented, so that it maybe modified for local use. Most of the +values in the file are for use with CAD-4 machines, but the +DFMODL flag and the VM microscope veiwing values are for general +use. + The program creates 4 other files at the request of the +user. + + 1. Another binary direct access file with records of 32 4 byte + variables which is used to store the reflection profiles if + wanted. This file can become very lengthy, if all profiles + are saved, even though the data is compressed, and it is + normally not necessary to save this data as profile analysis + is done on line as the data is being recorded. The file is + produced by setting switch 9 with the SW command. It has + the default name PROFL7.DAT. + + 2. The profile data on PROFL7.DAT can be transformed to ASCII + and written to a file with the default name PROFL7.ASC, + using the AP command. + + 3. The intensity data on IDATA.DA can be tranformed into ASCII + and written to a file with the default name IDATA.ASC, using + the AI command. + + 4. The IP command collects intensity data from psi scans of + 360ø in 10ø steps, and writes it to the file CURVES.DAT, for + use with empirical absorption calculations. ++ + +
+
+BD all Basic Data (includes CZ FR LA OM PS RO RR SD SE TM TP) + + This command takes the user through all the terminal input +commands necessary to establish a minimum valid set of basic +data. However, all parameters are assigned sensible default +values if a new IDATA.DA file is created when the program is +started, or current values are read from the existing IDATA.DA +file, therefore it is not usually necessary to use this command, +but rather alter specific parameters with individual commands. + + +CZ Correct angle Zero values + + Zero corrections, from AL or A8, may be typed. For the most +accurate work it is advisable to derive corrections for the +particular crystal, as they will vary with the optical centering +of the crystal. + + +FR First Reflection to be measured + + The h,k,l values of the first reflection to be measured can +be typed in, followed by the set and segment numbers (see GO) for +the reflection and the number of the first record of the IDATA +file which will be used. The GO command generates the first +reflection automatically at the start of data collection and +after an interruption if an automatic restart is possible. If +measurement conditions have been changed, then an automatic +restart is not possible and the user must supply the first +reflection information in the GO command, thus it is not +necessary to use the FR command. + +Example: + Command fr + First Reflection Data + Type h,k,l for the reflection 2,0,0 + Type the Reflection and Segment numbers 1,1 + Type the Data record number 20 + + +LA LAmbda for the wavelength in use, usually Ka1 + + It is preferable to use the Ka1 wavelength if profile +analysis is being used. If the mean Ka wavelength is preferred +it is advisable to set the dispersion parameter |la1 +la2|/mean(la) (in SD) to 0 to prevent the profile analysis +routine from starting its background search too far above the +peak on the high angle side and hence reaching wrong conclusions. + +Example: + Command la + Type the wavelength (0.70932) + + + +OM Orientation Matrix + + Prerequisites: LA, TM + + The orientation matrix may be typed in, but it is almost +always derived by OC, M2, M3 or MM. + + +PS PSi rotation data + + A y step, minimum y and maximum y are typed in. This +command is given either to collect data for empirical absorption +corrections, or in order to investigate possible multiple +reflections. All subsequent intensity measurements will be +affected by this command, including those in GO, therefore it is +advisable to set the y step back to 0ø once the requirement is +complete and before the GO command is given. For empirical +absorption purposes this command has largely been superseded by +the IP command. It is very useful for investigating multiple +reflection effects. + +Example: + Command ps + Psi Data: Dpsi,Psimin,Psimax 2,0,10 + + +RO Re Orientation reflections: frequency, tolerance and h,k,ls + + It is possible to set up a list of reflections which will be +used as for AL, to derive a new orientation matrix periodically +during data collection. This new matrix is accepted if the +average angular deviation between reflection vectors for the old +and new matrices is greater than a specified tolerance. + + Input consists of the frequency of re orientation, in terms +of the number of intervening reflections, as for RR, the angular +tolerance, and a list of h,k,l values. Each reflection typed in +and its Freidel equivalent will be aligned and the user can +select also to use symmetry equivalents, as for AL. This can +quickly generate a lengthy list and re orientation would then be +quite a lengthy procedure. Because of this it is best not to +enter more than about 12 well chosen reflections in total. + + Reorientation can be disabled by giving the frequency as 0. +Example: + Command ro + Perform re orientation during data collection (N) ? y + Type the re orientation frequency (500) + Type the re orientation angular tolerance (0.1) 0.2 + The following 13 reflections are in the AL/RO list + 1. 0 1 2 2. 0 1 2 3. 1 2 3 4. 1 +2 3 + 5. 3 2 1 6. 1 2 3 7. 1 2 3 8. 1 + 2 3 + 9. 1 2 3 10. 2 3 4 11. 2 3 4 12. 2 + 3 4 + 13. 2 3 4 + The following options are available : + U. Use the existing AL/RO list; + A. Add reflections to the existing AL/RO list; + D. Delete reflections from the existing AL/RO list; + N. New AL/RO list. + L. List the reflections in the existing AL/RO list; + E. Exit + Which option do you want (U) ? n + Friedel equivalents are always used. + Do you want symmetry equivalents as well (Y) ? n + Type h,k,l for up to 100 reflections + h,k,l (End) 1,2,3 + h,k,l (End) 4,3,2 + h,k,l (End) 3,4,2 + h,k,l (End) 4,5,1 + h,k,l (End) + The following 4 reflections are in the AL/RO list + 1. 1 2 3 2. 4 3 2 3. 3 4 2 4. 4 +5 1 + The following options are available : + U. Use the existing AL/RO list; + A. Add reflections to the existing AL/RO list; + D. Delete reflections from the existing AL/RO list; + N. New AL/RO list. + L. List the reflections in the existing AL/RO list; + E. Exit + Which option do you want (U) ? + + +RR Reference Reflections: frequency and h,k,ls + + The specified reference reflections (up to 6) are measured +after every N reflections for intensity control purposes. These +reflections should not be too intense, to avoid the use of +attenuators, and should be well distributed in reciprical space. +No attempt is made to monitor these reflections for fall off +because it is felt that significant change probably requires user +intervention. Changes are just as likely to be caused by crystal +translation, which cannot be corrected automatically, as by +rotation. + +Example: + Command rr + Measure reference reflections during data collection (Y) ? + Type the measurement frequency (100) + Type up to 6 sets of h,k,l values. + h,k,l > 2 + h,k,l > ,2 + h,k,l > ,,2 + h,k,l > + +SD Scan Data: type, width, scan speed, profile control + + Eight measurement types are available: + 0. Constant speed w/2q b/P/b scan; + 1. Constant speed w b/P/b scan; + 2. w/2q b/P/b scan with precision control; + 3. w b/P/b scan with precision control; + 4. Peak top with 2q backgrounds; + 5. Peak top with w backgrounds; + 6. Peak top with 2q backgrounds and precision control; + 7. Peak top with w backgrounds and precision control. + + Constant speed scans (types 0 and 1) are normal scans plus +extra background points, where the duration of the background +measurements is always specified (in TP) as a fraction of the +scan or peak time. If profile analysis is to be done (types 0 to +3) this fraction should be small, 0.1, meaning 0.1 of the scan +time is spent on background at each end of the scan. If it is not +to be done, the fraction should be larger, say 0.25. + + Precision control for types 2 and 3 is carried out using the +algorithm described in Grant,D.F., Acta Cryst., (1973), A29, +217). Precision measurements require the input of 3 parameters +(in TP) which are + (a) a maximum time to be spent on a single reflection, + (b) a "desired" precision, and + (c) a "minimum acceptable" precision. +The routine performs an initial scan and then decides whether the +"desired" precision has already been reached. If it has, it goes +on to the next reflection. If not, a decision is made whether +that precision can be reached within the maximum time and if so, +further scans are done to achieve this. If this "desired" +precision cannot be achieved, the routine decides whether at +least the "minimum acceptable" precision can be reached by +measuring for the full maximum time. If it can further +measurements are taken, if not, no more measurements are taken. + + While this controlled precision mode sounds attractive, for +many organic crystals it can lead either to spending long times +measuring weaker reflections or having many weak reflections +poorly measured because the routine decides it cannot attain the +minimum precision in the maximum time. A better way to improve +precision is to use the simpler scheme of measuring every +reflection at the same speed (types 0 or 1) and use additional +time to measure symmetry equivalents. This minimizes both random +(obscuration and collision) and systematic (absorption, +extinction, multiple reflection) errors. + + Peak top measurement (types 4 and 5) is done by measuring +for a fixed time at the calculated peak top position and a +fraction of this time at each background position. + + Peak top measurements with precision control (types 6 and 7) +work in a similar manner to the scan methods with precision +control. Again 3 values are needed from TP, + (a) maximum number of counts wanted, + (b) sample count time in seconds, + (c) maximum allowed time per reflection. +The peak top is measured for the sample time and from that a time +is derived which is either that required to reach the maximum +count, or the maximum time allowed. Counting is repeated, if +necessary, to reach either objective. + + + Peak top measurements are rarely used because the +instability of the crystal mount makes it difficult to ensure +that reflections are exactly in the centre of the detector over +long periods of time. Peak top measurements are bad practice at +TRICS because of the insecurity in determining the UB matrix +caused by the huge size of the peaks. + + Scan widths are specified as 3 parameters in the equation + Width = As + Bs*tanq + Cs, where + As is the angular width from the beginning of the scan to +the a1 position, + 360 |la1 la2| + Bs is the dispersion from a1 to a2 as . -- +, and + 2P mean(la) + Cs is the angular width from the a2 position to the end of +the scan. + +Typical values are 0.7, 0.7, 0.7 for MoKa and 1.0, 0.3, 1.0 for +CuKa. + + The scan speed for types 0 to 3 is given in ø/min. and this +speed is used for all measurements. + + Profile control consists of + 1. a flag indicating whether profile analysis is to be done for + types 0 to 3, where 0 means do it and 1 means don't, and + 2. if it is to be done, the fraction of As below the a1 + position, and of Cs above the a2, at which to start profile + analysis. This merely saves time by not trying to analyse + areas of the peak which will obviously not be flat. + + The type of profile analysis used is a slope detection +algorithm (Grant, D.F. and Gabe, E.J., J. Appl. Cryst. (1978), +11, 114), which looks for sensibly flat parts of the profile as a +statistical window is moved from the peak towards the ends of the +profile. Profile analysis can be performed as part of the data +collection process and it is suggested that this be used as the +routine mode of operation. Profile analysis improves the quality +of intensity data in two ways. + + 1. The precision of background measurements is improved by + including a greater fraction of the peak in the background. + 2. The precision of the net intensity is improved by reducing + the amount of background under the narrowed peak. + + Reflection profiles are routinely displayed on the screen, +whether or not profile analysis is requested, together with the +theoretical a1 position. When analysis is requested, the +intensity weighted maximum position is shown and also the points +at which the routine decides to separate peak from background. + + When profile analysis is requested, the routine takes +background measurements at each end of the scan for a small +fraction of the scan time, usually 0.1, in order to decide if the +peak is significant and therefore analysable. If it is, analysis +is done and profile points outside the high and low scan limits +obtained are added to the backgrounds and a new overall +fractional background time established. This means both improved +background measurements and a reduced amount of background under +the peak because of reduced peak width. Thus either a given +overall precision can be achieved in a shorter time or improved +precision in a fixed time. + + For CAD 4 machines a flag can be set which will cause the + , , reflection to be used if there is obscuration at high 2q +and c values for the normal +,+,+ reflection. + +Example: + Command sd + Scan data : Scan type, As,Bs,Cs, Profile flag. + + Scan type: 0 2Theta, 1 Omega, + 2 2Theta precision, 3 Omega precision, + 4 2Theta peak top, 5 Omega peak top, + 6 2Theta econ. pktop, 7 Omega econ. pk top; + Type the scan type (0) + Reflection width in degs is As + Bs*tan(theta) + Cs + Type the new As, Bs, Cs ( 0.500 0.000 0.500) .7,.3,.7 + Profile flag 0/1 for DO/DONT DO profile analysis. + Type the flag (0) + Scan Step and Preset (4) + Try , , refln if high angle scan problems (Y) ? + Fraction of A & C to step off for profile analysis (0.5) + + +SE Systematic Extinctions + + This command originally allowed the user to specify +extinction conditions, but it has largely been superseded because +the SG command now detects absences automatically. However, it +can still be useful to setup non space group conditions if the +need arises. This is done by telling the routine which class of +reflections the condition applies to and then specifying the +coefficients A to E of the conditional equation + Ah + Bk + Cl = Dn + E +for the reflection to be considered present. Reflection classes +are + 1 00l 2 0k0 3 h00 4 0kl 5 h0l 6 hk0 7 hkl + + Suppose for example in a superstructure only reflections +with h = 3n are to be measured, then the condition would be + + Class A B C D E + 7 1 0 0 3 0 + + +SG Space Group symbol + + Several of the options of DIFRAC need symmetry information, +e.g. IE, GO, AL. The SG command interprets the standard form of +a space group symbol to calculate symmetry matrices in order to +be able to generate equivalent reflections. The symbol is typed +with blanks separating distinct operators, e.g. P 21/c or P 21 +21 21 or P 63/m c m. + + Apart from generating equivalent indices, the symmetry +information allows subsequent routines to detect systematic +absences and Friedel reflections. It also allows the segment(s) +of reciprocal space which form the unique set to be generated +(see the description of DH sets under GO) and if wanted +equivalent unique sets. For data collection all the routine +really needs is the Laue group symbol, but it cannot then detect +translational systematic absences. Currently there is a limit of +24 symmetry operations. Beware of high symmetry space groups! + + +Example: + Command sg + Type the space group symbol (P 1) f d d 2 + Space Group F D D 2 + The Space Group is ACentric F Centered Orthorhombic Laue +Symmetry mmm + Multiplicity of a General Site is 16 + The location of the origin is arbitrary in z + + Space group Equivalent Reflections are: + h k l h k l + h k l h k l + Friedel Reflections are the , , of these. + + +TM 2q Minimum and maximum values + + Because of the use of DH matrices, which minimize the time +needed to collect a unique set, it is not normally necessary to +collect data in 2q shells. Thus it is usual to input one pair of +values, say 2ø to 50ø, for MoKa, to control the range of data +collection. If at the end of this, it is felt that it would be +useful to collect more data, further shells can be collected. +The defaults indicated are the current values. + +Example: + Command tm + Type 2Thetamin and 2Thetamax ( 2.00, 80.00) + + +TP Time and Precision parameters for intensity measurement + +Prerequisite: SD + + The value for the background fraction is requested for all +measurement types except peak top with precision (types 6 & 7). +This fraction is the ratio of the time for one background +measurement to the time for the peak measurement. + + If the scan type is w/2q or w (types 0 and 1) only the value +for the background fraction is requested. Suggested values are +0.1 with profile analysis, 0.25 with no profile analysis. + + If controlled precision measurement is being used (types 2 +and 3), 3 further parameters are requested as explained under SD. +Care should be taken to give reasonable values so that large +amounts of time are not spent measuring for little return. +Suggested values are 240 secs maximum time, 0.01 desired +precision i.e. 1%, and 0.10, i.e. 10% minimum acceptable +precision. + + If peak top measurements are selected (types 4 and 5) one +further value is needed for the peak counting time. A suitable +value is 5 secs. + + If peak top measurements with precision are selected (types +6 and 7) 3 values are needed as explained under SD. Sensible +values are 10000 maximum count, 1.0 second sample time and 10 +seconds maximum time. + +Example: + Command tp + Time and Precision Parameters + Type the Background fraction (0.1) ++ +
+
+AL ALign reflections and symmetry equivalents for MM + +Prerequisites: LA, Valid matrix + + Values of h,k,l are typed and equivalent reflections can be +generated if wished. These and their Friedel equivalents will be +centred (see CR) and the results stored on file for subsequent +use with MM. + + This command is meant primarily to provide the data for +accurate cell parameters at the end of a data collection run, +using suitable reflections found with the BI command. Up to 200 +equivalent reflections, counting Friedel and symmetry +equivalents, may be stored in the h,k,l lists. It is often +useful to align the + and Friedel equivalents only, to +establish an improved orientation matrix prior to data +collection. In this case choose not to use symmetry equivalents. +It is also possible to use 4 geometrically equivalent settings +for each reflection in order to eliminate the 2q and c zero +errors. If AL is interrupted with K, the process stops when the +current reflection centreing is finished. It can be resumed with +AR. + +Example: + Command al + Alignment of Symmetry and Friedel Equivalent +Reflections + + The following 5 reflections are in the AL/RO list + 1. 10 0 0 2. 0 10 0 3. 0 16 0 4. 16 +0 0 + 5. 0 0 16 + The following options are available : + U. Use the existing AL/RO list; + A. Add reflections to the existing AL/RO list; + D. Delete reflections from the existing AL/RO list; + N. New AL/RO list. + L. List the reflections in the existing AL/RO list; + E. Exit + Which option do you want (U) ? n + Friedel equivalents are always used. + Do you want symmetry equivalents as well (Y) ? + Align 4 equivalent settings for each reflection (N) ? + Type the space group symbol (P 4/M) + Type h,k,l for up to 100 reflections + h,k,l (End) 1,2,3 + 1 2 3 2 1 3 1 2 3 2 1 +3 + h,k,l (End) 3,2,1 + 3 2 1 2 3 1 3 2 1 2 3 +1 + h,k,l (End) + The following 8 reflections are in the AL/RO list + 1. 1 2 3 2. 2 1 3 3. 1 2 3 4. 2 +1 3 + 5. 3 2 1 6. 2 3 1 7. 3 2 1 8. 2 +3 1 + The following options are available : + U. Use the existing AL/RO list; + A. Add reflections to the existing AL/RO list; + D. Delete reflections from the existing AL/RO list; + N. New AL/RO list. + L. List the reflections in the existing AL/RO list; + E. Exit + Which option do you want (U) ? + + At this point the results of the reflection alignment will +be output to the printer. + +Starting Values 1 2 3 15.251 0.000 53.30 63.435 +Final Values 15.263 359.983 53.256 63.435 +Starting Values 1 2 3 15.251 0.000 306.699 243.435 +Final Values 15.240 359.979 306.719 243.435 + ................................................ + ................................................ +Starting Values 2 3 1 15.251 0.000 344.499 303.690 +Final Values 15.236 0.019 344.534 303.690 + + +AR Align Resumption after interruption + +Prerequisite: AL + + As the AL command can be rather time consuming, it is +sometimes necessary to interrupt it and resume later. AR allows +this to be done and the alignment process resumes exactly where +it was interrupted with K. + + +A8 Align the 8 equivalent settings of 1 reflection for angle +zeroes + + On a 4 circle instrument any reflection can in principle be +set at the 8 positions + + 1. +2q w c f 2. +2q w c 180+f + 3. +2q w 180 c 180+f 4. +2q w 180+c f + 5. 2q w c f 6. 2q w -c 180+f + 7. 2q w 180 c 180+f 8. 2q w 180+c f + + Once the 8 settings have been centred, instrumental zeroes +for 2q, w and c are calculated, as well as crystal and detector +height adjustments. It is best to use results from several +reflections and take the average values. + + In practice the best c value to choose is near n*45ø. +However, on kappa geometry goniometers only reflections with c +in the range 80ø to 100ø. are accessible and these can be found +with the BC command. On CAD 4 machines the instrument alignment +corrections DET, HOR, VER and MON (see the CAD 4 manual) are +calculated and printed. + +Example: + Command a8 + 8 Reflection Centring (Y) ? + (The next 3 lines are for non CAD 4 machines only) + Type the 2T,Om,Ch step size in 1/100th ( 4, 2,10) + Type the count time per step in seconds (1.0) + Type the max count cutoff fraction (0.5) + Type h,k,l for reflections to be used (End) + Next h,k,l (End) 2 0 0 + Next h,k,l (End) + Is everything OK (Y) ? + + The following type of output appears on the screen and the +printer + +Starting values 1 1 12 24.582 357.229 97.466 +359.819 + Final values 24.597 357.095 97.412 +359.819 564 +Starting values 1 1 12 335.418 357.229 97.466 +359.819 + Final values 335.409 357.105 97.360 +359.819 575 +Starting values 1 1 12 24.582 2.771 82.534 +179.819 + Final values 24.595 2.688 82.421 +179.819 537 +Starting values 1 1 12 335.418 2.771 82.534 +179.819 + Final values 335.386 2.690 82.357 +179.819 502 +Starting values 1 1 12 24.582 352.525 272.747 +90.179 + Final values 24.571 352.420 272.647 +90.179 521 +Starting values 1 1 12 335.418 352.525 272.747 +90.179 + Final values 335.370 352.429 272.573 +90.179 548 +Starting values 1 1 12 24.582 7.475 267.253 +269.821 + Final values 24.578 7.336 267.085 +269.821 733 +Starting values 1 1 12 335.418 7.475 267.253 +269.821 + Final values 335.373 7.360 267.167 +269.821 721 +Zero Values of TT,OM,CH .015 .109 .122 +Offsets: Det .029mm, Hor .021mm, Ver .059mm, Mon .016deg. +True 2Theta Omega Chi Phi + 24.600 2.768 97.480 .000 + +CH CHoose reflections from the PK list for use with M2 or M3 + + Reflections may be selected from the list produced by PK, if +their indices are known, for use with M2 or M3 to derive an +orientation matrix. + +Example: + Command ch + Choose reflections from OC for M2 or M3 (Y) ? + Sequence number in OC and indices + Reflection 1 1 0 0 3 + Reflection 2 2 0 4 0 + Reflection 3 4 5 1 1 + + +CR Centre the Reflection which is already in the detector + + The reflection which is presently in the detector is centred +in the aperture. It does not have to be an indexed reflection +and so CR can be used at any time. + + The centring algorithm for Euler instruments searches for +half height on both sides of the peak as the circles are stepped +consecutively, retaining the counts for each step. Once the half +heights on both sides are found, the centre of the distribution +of counts is found as the "best" position. Circles are adjusted +in the order w, 2q, c, w, 2q. For precise work it is advisable +to restrict the detector aperture with narrow horizontal and +vertical slits. For initial setup normal apertures from +collimators are usually sufficient. The step size for each circle +can be set, with defaults of 4/100ø, 2/100ø and 10/100ø for 2q, w +and c, f is held constant. Recommended setting for TRICS are +4,4,40 for the steps. The fraction to use as "half height" can be +input, as can the count time/step. Defaults are 0.5 and 1 sec. + + If the peak was sensibly in the centre of the detector +aperture at the start of the centreing process, then usually only +a few steps are needed in each direction to find both +half heights and hence the centre. If the peak is displaced so +that it lies within 50 steps above or below the centre, the +routine detects this and finds the centre from one side of the +stepping process. If the peak is at one of the extreme ends of +the +/ 50 step process, the routine adjusts the assumed centre to +the appropriate end and repeats the process. If no significant +peak is found within +/ 50 steps, an error message is printed. + + For kappa instruments centring is achieved with a continuous +2q scan followed by scans with 45ø slits. Again there are +safeguards to ensure that badly displaced peaks are brought +nearer to their "best" position, with a series of step scans and +then the normal centring process is repeated. + + These algorithms are used for all centring operations (AL +and A8). + +Example: + Command cr + Centre the reflection already in the detector + Is the reflection already set (Y) ? + Type h,k,l for use in M2/M3 1 2 3 + +Starting Values 1 2 3 15.251 0.00 53.301 63.435 +Final Values 15.243 0.008 53.256 63.435 + + +LC 2q Least squares with symmetry Constrained cell + + The unit cell derived from the matrix produced by MM is +necessarily triclinic, though hopefully it should agree with any +known symmetry, within the standard deviations. LC is a command +to use only the 2q values from the AL list and a specified +crystal symmetry to produce the optimal unit cell consistent with +the data and the imposed symmetry. (Note the non standard +space group setting used below is accepted). + +Example:- + Command lc + + Constrained Cell Dimension Least Squares + + Type the space group symbol (P 4/m) P 2/m 1 1 + +Wavelength .709320; 38 reflections. + Cell Errors + a 9.566021 .0002590 + b 9.930408 .0033505 + c 6.582347 .0003861 + Alpha 100.260 .0148 + Beta 90.000 .0000 + Gamma 90.000 .0000 + + +MM Matrix from Many reflections by least squares on AL data + + With a minimum of 4 reflections, preferably more, a matrix +can be calculated with least squares, and a unit cell and +standard deviations derived. The input data is usually taken +from the list produced by AL, which can be edited and/or added +to, before use. The data can also be typed in, though this is +very tedious. Zero corrections are derived for w and c. These +should be close to zero if the values used in CZ are accurate. +If they are not then zeroes should be checked with A8, corrected +with CZ and MM run again. + +Example: + Command mm + Least Squares Orientation Matrix (Y) ? + Reflection data can be on file or from the terminal. + Wavelength (0.70932) + Read the data from the terminal (N) ? + Reflections may be deleted or restored to the list by typing : + h,k,l,1 for Delete or h,k,l,0 for Restore. CR = End. + > + Do you wish to insert reflections (N) ? + +Omega(0)is .008 from 19 reflections. +Chi(0) is .014 from 0 +/ pairs. +Select a number for the cell geometry to be used +Triclinic 1 Monoclinic 2 +Orthorhombic 3 Tetragonal 4 +Hexagonal 5 Rhombohedral 6 Cubic 7 +Type your selection (2) + +The following output appears on the printer + + Orientation Matrix from 19 Reflections + 0.00050366 0.06722744 0.13259950 + 0.10452530 0.00104539 0.00204850 + 0.00185812 0.07713195 0.07905444 + + Observed Calculated +Angular + h k l 2Theta Omega Chi Phi 2Theta Omega Chi +Ph Deviation + 0 3 0 12.50 .00 48.92 180.89 12.50 .00 311.08 +180.89 0.012 + 4 0 0 17.06 .00 1.02 89.72 17.06 .00 358.98 +89.72 0.034 + +........................................................ + +........................................................ + 1 2 2 14.44 .00 62.44 36.85 14.44 .00 97.56 +36.85 0.027 + 1 2 6 38.02 .00 43.35 7.76 38.02 .00 316.65 +7.76 0.036 + + Real Cell + a b c alpha beta gamma + 9.56544 9.93189 6.58240 100.263 89.999 89.999 + .00038 .00129 .00024 .007 .003 .007 + + Reciprocal Cell + a* b* c* alpha* beta* gamma* + .104543 .102323 .154390 79.737 90.002 90.001 + .000004 .000013 .000004 .007 .003 .007 + + +M2 Matrix from 2 indexed reflections and a unit cell + + If the unit cell is known, then the crystal orientation and +hence the matrix can be calculated from the angular settings of 2 +indexed reflections. This can be useful if details of the unit +cell and some reflections are known from PK or any other source. +The reflection data can be typed in as h,k,l, w, c, f or selected +from the PK list with CH. + +Example: + Command m2 + Orientation Matrix from Cell + 2 Reflections (Y) + Type the wavelength ( .70932) + Type a,b,c,alpha,beta,gamma 9.5654 9.9319 6.5824 100.26 90 90 + Are angles to be typed (Y) ? n + The two reflections being used are + 0 3 0 .000 48.923 180.892 + 4 0 0 .000 1.019 89.725 + Do you wish to edit the reflection indices (Y) ? n + Select a number for the cell geometry to be used + Triclinic 1 Monoclinic 2 + Orthorhombic 3 Tetragonal 4 + Hexagonal 5 Rhombohedral 6 Cubic 7 + Type your selection (2) 2 + +The following output appears on the printer + + Orientation Matrix from M2 + 0.00050312 0.06722458 0.13259660 + 0.10452580 0.00104658 0.00204272 + 0.00185683 0.07713310 0.07905647 + + +M3 Matrix from 3 indexed reflections + + As for M2, a matrix can be calculated from the known indices +and setting angles for 3 reflections. The reflection data can be +typed in as h,k,l, 2q, w, c, f or selected from the PK list with +CH. + +Example: + Command m3 + Orientation Matrix from 3 Reflections (Y) ? + Type the Wavelength (0.70932) + Are the angles to be typed (N) ? + The three reflections being used are + 0 3 0 12.501 0.000 48.923 180.892 + 4 0 0 17.057 0.000 1.019 89.725 + 1 1 5 31.594 0.001 38.164 8.890 + +The following output appears on the printer + + RIGHT handed Orientation Matrix from M3 + 0.00050082 0.06722900 0.13259690 + 0.10451990 0.00104665 0.00204341 + 0.00185934 0.07713817 0.07906044 + +a* .10454 b* .10233 c* .15439 Alf* 79.741 Bet* 90.001 +Gam* 90.002 +a 9.56593 b 9.93121 c 6.58228 Alf 100.259 Bet 90.000 Gam +89.998 + +OC Orient a Crystal i.e. index the peaks from PK + + This command uses a modified version of Jacobsen's indexing +routine (Ames Lab. Report, IS 3469,1974) to find a cell which is +consistent with all the reciprocal lattice vectors found by PK. +The algorithm searches for the triple of minimum non coplanar +vectors which will give essentially integer h,k,l values to all +the input vectors. The algorithm is extremely robust and will +always produce a cell and orientation matrix with reasonable +data. In case of difficulty the list from PK may be edited, +usually to remove weak reflections which maybe arise from +satellite crystals, or other known peaks can be added. It is +also possible to read in sets of 2q, w, c, f from a file called +REFL.DAT. + + As with all other indexing algorithms, the routine cannot +overcome deficiencies in the data. For example, if the data only +contains reflections with h = 2n, then the cell produced will +have a dimension a/2. + + The cell produced is of course not necessarily the reduced +cell, though it often is, and the routine can automatically +invoke the reduction algorithm (RC) and then reset the crystal +(RS) if necessary. Once this is done, the routine automatically +invokes the MM least squares procedure to produce an optimized +orientation matrix and unit cell from the PK list with reduced +cell indexing. + +Example: + Command oc + Index Reflections and derive an Orientation Matrix + 1) Index reflections in the list from PK + 2) List and edit the reflections + 3) Cancel + + Enter option (1) 2 + There are 39 peaks in the list + (L) List the reflections; + (D) Delete a reflection; + (R) Reinsert a reflection; + (A) Add a reflection; + (F) Read reflections from a file; + (E) Exit. + Command (L,D,R,A,F,E) f + Type the reflection file name (REFL.DAT) + Subtract theta from the omega value (N) ? + 44 reflections have been read from REFL.DAT + Command (L,D,R,A,F,E) e + Do you want to index the reflections (Y) ? + Error Limit = 0.10 + + Cell Dimensions: + a 6.916, b 6.920, c 6.901 + alpha 119.98, beta 119.63, gamma 60.10. Volume = 234.37 + + + h k l h k l h k l h k l + 1 1 0 1 1 0 0 1 2 0 1 2 + 2 2 1 2 2 1 1 1 1 1 1 1 + 1 2 0 1 2 0 1 0 2 2 0 0 + 1 1 1 1 1 1 2 0 1 2 0 1 + 1 1 1 1 1 1 0 0 2 2 2 0 + 2 2 0 0 3 1 2 1 1 2 1 1 + 1 1 2 3 1 0 3 1 0 1 2 1 + 2 0 3 2 0 3 3 0 0 3 2 0 + 3 2 0 2 1 2 2 1 2 3 1 3 + 1 2 2 2 2 0 1 2 3 0 1 4 + 4 4 2 4 4 2 2 4 0 2 2 2 + + Orientation Matrix: + 0.044395 0.123749 0.155932 + 0.167463 0.074546 0.002795 + 0.033644 0.102249 0.083725 + + Cell Reduction Step + +Type the Allowable Tolerance on True Cell Angles (0.1deg) +Lattice Type (P) ? + +Input Cell: 6.916 6.920 6.901 119.977 119.632 +60.102 + Lattice Type P + + The Shortest Non coplanar Translations + 6.901 6.913 6.916 90.309 119.632 +119.875 + The Old to New Cell Matrix + 0.0 0.0 1.0 + 0.0 1.0 1.0 + 1.0 0.0 0.0 + + Possible 2 fold Axes: + Rows Products Kind + Direct Reciprocal Dot Vector of Axis + 1 1 0 1 1 1 2 0.145 2 + 1 0 1 1 1 1 2 0.180 2 + 0 1 1 0 1 1 2 0.223 4 + 0 1 1 1 1 1 2 0.231 4 + 0 1 0 1 2 0 2 0.309 2 + 2 1 1 1 0 0 2 0.319 4 + 1 0 0 2 1 1 2 0.345 2 + 1 1 1 0 1 1 2 0.360 2 + 0 0 1 1 0 2 2 0.444 2 + 2 1 3 0 0 1 3 0.117 3 + 2 1 1 1 1 0 3 0.155 3 + 2 1 1 1 0 1 3 0.086 3 + 2 3 1 0 1 0 3 0.060 3 + + # 1 Pseudo Cubic F Max Delta 0.444 + a 1.0 1.0 1.0 9.8055 Alpha 90.025 a* 0.000 + 0.500 0.500 + b 1.0 1.0 1.0 9.8044 Beta 89.770 b* 0.500 + 0.500 0.000 + c 1.0 1.0 1.0 9.7516 Gamma 90.222 c* 0.500 +0.000 0.500 + # 2 Pseudo Hexagonal R Max Delta 0.345 + a 0.0 1.0 0.0 6.9197 Alpha 90.249 a* 0.667 + 1.000 1.000 + b 0.0 1.0 1.0 6.9126 Beta 90.088 b* 0.333 +0.000 1.000 + c 3.0 1.0 1.0 16.9989 Gamma 120.148 c* 0.333 +0.000 0.000 + # 3 Pseudo Tetragonal I Max Delta 0.319 + .......................................................... + .......................................................... + # 7 Metrically Triclinic P Max Delta 0.000 + a 0.0 0.0 1.0 6.9007 Alpha 90.309 a* 0.000 + 1.000 1.000 + b 0.0 1.0 1.0 6.9126 Beta 119.632 b* 0.000 + 1.000 0.000 + c 1.0 0.0 0.0 6.9157 Gamma 119.875 c* 1.000 +0.000 0.000 + + These transformations are also output to the printer for +checking before answering the following question, + + Which transformation do you wish to use (1) ? 2 + + The data is then submitted to least squares with output sent +to the printer as described under MM. The question + + Do you want to replace the old matrix with this new matrix (N) ? +y + +allows the user to : + +a. retain the existing matrix, in which case no further action is +taken, or +b. accept the new matrix, in which case the following appears on +the terminal + + Space group choices are as follows : + 1. The safest space group based on cell reduction R 3 + 2. The safest space group based on cell lengths P 1 + 3. Any other space group. + Which do you want (1) + +PK PeaK search in 2q, c, f for use with OC + + This is the normal and simplest way to orient an unknown +crystal. Ranges of 2q and c are given, together with step sizes, +and the diffractometer then rotates f through 180ø at each step +as it searches through the c and 2q ranges, until the specified +number of peaks have been found and centred, or the search range +is exhausted. The reason for searching only 180ø in f is an +attempt to maximize the c range for crystals with large unit +cells, when many reflections may be found quickly in a narrow +range. No reflections will be missed, but if the c range extends +equally in both directions about zero with 360ø scans, both the ++h,+k,+l and h, k, l equivalents would be found. + + This command, with all the accompanying centring, can be +quite lengthy and it is therefore best not to ask for too many +peaks. The PK command goes directly into an OC procedure and 10 + 15 peaks are usually sufficient for unambiguous operation. The +command can be interrupted with K and, if necessary, resumed +again with PK, indicating that it is not a new search. + +At TRICS it is recommended to use at least 15 degrees as step for +chi as peaks can be 10-15 degrees wide in chi at TRICS. + +Example: + Command pk + + Routine to Search for Reflection Positions + + Is this a new search (Y) ? + 2 theta search: min, max, step (10,30,4) 15,31,4 + Chi search (allowed range 90 to +90) + min, max, step ( 50,50,10) + How many peaks do you want to find (20) ? + Is everything OK (Y) ? + + The following output of coarse positions appears on the +terminal and printer + + 2Theta Omega Chi Phi INT + 1 15.00 .00 320.00 73.00 779. + 2 15.00 .00 .00 85.00 310. + ........................................... + ........................................... + 18 31.00 .00 40.00 35.00 165 + 19 31.00 .00 40.00 5.00 42 + + 19 new peaks were found before the end of the search + + The routine then centres these peaks accurately and the +following output appears on the printer only. The fifth number +on the Final Values line is the intensity for a 1 second count at +the peak position These values including the intensity are +stored for submission to MM or LC. + +Peak 1 Coarse Setting 14.999 .002 320.001 73.000 + Approximate 14.818 .092 320.549 72.920 + Final Values 14.816 .085 320.571 72.920 +7829 + +............................................................ + +............................................................ +Peak 19 Coarse Setting 30.999 .001 40.001 5.000 + Approximate 30.750 .126 40.683 3.860 + Final Values 30.730 .164 40.735 356.140 +353 + + +RC Reduce a unit Cell + + Cells from LC, M3, MM, OM or OC, can be reduced [Le Page Y., +J. Appl.Cryst. (1982), 12, 255] using an algorithm to find 2 fold +axes. It does this by imposing artificial 2 fold axes on the +reciprocal lattice, in all non redundant directions with indices +less than 3. If the new lattice points generated by these +imposed 2 fold axes coincide, within a tolerance, with points on +the original lattice, then the direction is at least a possible +metric 2 fold axis. The results of this process, i.e. a set of +possible 2 fold axes, are analysed, both in terms of the original +symmetry and in terms of possible distributions of 2 fold axes in +all allowable symmetries. Any additional symmetry is noted and +the necessary transforms printed. + + This is an extremely robust algorithm and has never (yet) +been known to fail. If the input cell is in some way +non primitive the routine cannot, of course, account for this, +e.g. an axis was given at half its true length. If the routine +detects several possible unit cells with increasing symmetry, the +user is allowed to choose one to reset the cell and matrix +correspondingly and re index the reflections in the list. + +Example: + Command rc + Type the Allowable Tolerance on True Cell Angles (0.1deg) + Lattice Type (P) ? + + The screen and printer output are identical to the cell +reduction stage of the OC command + + +RP Rotate f 360, centre and save any peaks found + + This command, which is really the basis of the PK search, +rotates f 360ø in 1.8ø steps and then detects the peaks found, if +any. It then does a coarse centring of each, as the initial +value of f can be very imprecise, followed by a fine centreing as +in CR. This command has been largely superseded by PK. + + +RS ReSet the cell and matrix with the results from RC (similar +to TO) + +Prerequisite: RC + + The cell and matrix can be reset manually using the results +from RC, but a simpler and safer way to do this is to rerun OC, +automatically run RC and choose the correct transformation. + +Example: + Command rs + Reindex 3 Reflections (Y) ? + Reflection 1. Type OLD indices then NEW indices 0 0 1 1 0 0 + 0 0 1 6.28 .00 30.80 179.12 New indices 1 0 +0 + Reflection 2. Type OLD indices then NEW indices 1 0 0 0 1 0 + 1 0 0 4.25 .00 358.98 89.72 New indices 0 1 +0 + Reflection 3. Type OLD indices then NEW indices 0 1 0 0 0 1 + 0 1 0 4.16 .00 311.08 180.89 New indices 0 0 +1 + Type the Wavelength ( .70932) + +The new matrix and cell are output to the printer. ++ +
+
+GO Start of intensity data collection + + Pre requisites: CZ LA RO PS RR SD (SG) SW TM TP + Orientation matrix from MM(AL) M2 M3 or OC + + This command starts, or resumes, data collection using +parameters given under the pre requisite commands to control the +measurement conditions. If the space group has not been given +under SG, it is asked for. The user is queried about measuring +any translation element absences from screws and glides, and +lattice mode absences, if any. It is probably good practice to +measure the former for later checking, but not the latter. + + If data collection is being resumed after an interruption, +the routine checks to see whether an automatic restart is +possible, i.e. no parameters have been changed. If so it then +asks whether the user wishes to restart automatically. + + DH Matrices + + The sequence in which reflections are generated is +controlled by a set of so called DH matrices. These are 3x3 +matrices which describe segments of reciprocal space which +comprise the unique data set. They are described in Le Page Y. & +Gabe E.J., J. Appl. Cryst. (1979), 12, 464. + + The basic idea is that the segment or segments of reciprocal +space which form the unique set are described by 3x3 matrices +which specify the segment edges, plus a vector to specify the +segment origin. Thus, the matrix 1,0,0 / 0,1,0 / 0,0,1 describes +the segment with edges a*, b* and c*. These matrix and vector +pairs can be transformed by the symmetry matrices to generate +equivalent segments for further data sets. There are several +advantages to this approach. + + Firstly, reflections can be generated within any segment by +simple unit increments on a three dimensional grid and then +transformed to the true indices with the DH matrix. The +monoclinic system provides a good illustration. Two matrices and +origin vectors are needed to describe the complete unique set + + 1, 0, 0 / 0, 1, 0 / 0, 0, 1 0, 0, 0 (for +h,+k,+l) + 1, 0, 0 / 0, 1, 0 / 0, 0, 1 1, 0, 1 (for +h,+k, l) + +On the unit grid, the triple 1,2,3 is transformed by the first +pair as but with the second pair it is transformed as + +A second example in the cubic Laue group m3m where there is only +one matrix/origin pair + + 1, 0, 0 / 1, 1, 0 / 1, 1, 1 0, 0, 0 + +shows that in this case the same triple 1,2,3 transforms as + + Thus the same indexing scheme can be used for all +space groups. + + A second advantage is that the order in which the +reflections are generated can be changed easily by swapping the +rows of the DH matrix without changing the basic index generating +scheme. The matrix + + 1, 0, 0 / 0, 1, 0 / 0, 0, 1 + +implies that the segment of reciprocal space bounded by the 3 +reciprocal axes a*, b* and c* forms the segment of data to be +collected and the order of data collection is h slowest and l +fastest. It may happen, because there is a short reciprocal axis +for example, that it is more economical in time to increment that +axis fastest, in which case the matrix may be typed in the order +required, e.g. if b* is shortest and c* longest, the appropriate +DH matrix is + + 0, 0, 1 / 1, 0, 0 / 0, 1, 0 + +which would generate reflections, within the 2q limit, in the +order 0,0,0 to 0,kmax,0, then 1,kmax,0 to 1,0,0, then 2,0,0 to +2,kmax,0 etc, until all the h,k,0 rflections have been collected. +The process then starts again at the 0,0,1 reflection, and then +0,0,2 etc until all +h,+k,+l reflections have been collected. + + A third advantage is that the unique portion of reciprocal +space to be measured is specified exactly, i.e. with no +repetition of reflections. The monoclinic example above shows +that the reflections hk0 and 0kl are generated in the first +segment, but the reflections hk0 and 0kl are avoided in the +second by specifying the origin as 1,0,1. + + +The origin vectors and DH matrices which will measure the unique +set for all +Laue groups are as follows. + + Laue Origin DH Matrix + + 1 0 0 0 1 0 0 0 1 0 0 0 1 + 1 0 1 1 0 0 0 1 0 0 0 1 + 1 1 0 1 0 0 0 1 0 0 0 1 + 0 1 1 1 0 0 0 1 0 0 0 1 + + 2/m 0 0 0 1 0 0 0 1 0 0 0 1 + 1 0 1 1 0 0 0 1 0 0 0 1 + + mmm 0 0 0 1 0 0 0 1 0 0 0 1 + + 4/m 0 0 0 1 0 0 1 1 0 0 0 1 + 1 2 0 0 1 0 1 1 0 0 0 1 + + 4/mmm 0 0 0 1 0 0 1 1 0 0 0 1 + + R 3 0 0 0 1 0 0 1 0 1 1 1 1 + 1 1 0 1 0 1 0 0 1 1 1 1 + 0 1 2 1 0 0 1 0 1 1 1 1 + 1 0 2 1 0 1 0 0 1 1 1 1 + + R 3m 0 0 0 1 0 0 1 0 1 1 1 1 + 1 1 0 1 0 1 0 0 1 1 1 1 + + 3 0 0 0 1 0 0 1 1 0 0 0 1 + 1 2 0 1 1 0 0 1 0 0 0 1 + 0 1 1 0 1 0 1 1 0 0 0 1 + + 31m 0 0 0 1 0 0 1 1 0 0 0 1 + 0 1 1 0 1 0 1 1 0 0 0 1 + + 3m1 0 0 0 1 0 0 1 1 0 0 0 1 + 1 1 1 0 0 1 1 0 0 0 0 1 + + 6/m 0 0 0 1 0 0 1 1 0 0 0 1 + 1 2 0 0 1 0 1 1 0 0 0 1 + + 6/mmm 0 0 0 1 0 0 1 1 0 0 0 1 + + m3 0 0 0 1 0 0 1 1 0 1 1 1 + 1 2 0 0 1 0 1 1 0 1 1 1 + + m3m 0 0 0 1 0 0 1 1 0 1 1 1 + + + Having measured a unique set the routine will go on to +measure equivalent sets if allowed to. These sets are generated +in the order set 1, then the Friedel related set 1, then the +first equivalent set 2, then set 2, etc until the whole sphere +is measured. + + This is all transparent to the user with the SG and GO +commands, and measurement can safely be interrupted and restarted +automatically. + + Data collection always starts with the collection of a set +of reference reflections, which are printed to hard copy, along +with details of when they were taken. Reflections are generated +and measured according to the sequence controlled by the DH +matrices. Reference reflections are also taken and printed at +the start and end of each segment. Unique sets of data are +numbered sequentially 1, 2, 3 etc. with Friedel sets numbered 1, + 2, 3 etc. Thus in the monoclinic case with two DH matrices +(segments) the numbering scheme would be + + 1. Set 1, segments 1 and 2; 2. Set 1, segments 1 and 2; + 3. Set 2, segments 1 and 2; 4. Set 2, segments 1 and 2. + + This would then have measured the whole of the reciprocal +sphere, if allowed to proceed that far. The process can be +interrupted at any point with K or Q. During data collection all +reflection profiles are displayed on the screen, with the results +of profile analysis if selected, plus a short printout of results +on the screen. + + Data Collection Output + + Reflection results can be printed to hard copy using +switches 4 and 5 (see the SW command). Switch 4 is used for +normal reflections and switch 5 for reference reflections. The +default is to print both. + + Printout during data collection is as follows : + +At the start of each set of measurements a printer message gives + + h k l Reflection Set Segment Record, where + + h k l is the next normal reflection to be measured, + Reflection is the sequence number of the reflection, + Set is the number of the present set, + Segment is the number of the present segment, + Record is the record number on the .ID file. + + +For non reference reflection measurements (Printer SW4 = 0) + + On terminal (and printer) h k l Inet s(Inet) + if Inet < 2*s(Inet) h k l Inet s(Inet) ** + +For reference reflection measurements (Printer SW5 = 0) + + Terminal output is + h k l Peak s(Peak) N, where + N is the reference reflection number. + + Profile analysis is never done on the reference reflections, +though the profile is displayed, and all values are based on the +background time fraction given in TP. Reference reflections are +taken at the start and end of each segment and at intervals of N +reflections, as specified in RR. +For normal scan modes printer output is: + + N h k l 2q Scan time Natt b1 Peak b2 Inet, where + N is the reference reflection number, + Scan time is the time for the scan in seconds, + Natt is the attenuator index (normally 0), + b1,Peak,b2 low angle background, peak and high angle +background for the + parameters given in TP and SD + Inet is the net count, including any attenuator factor +which puts all + measurements of the same reflection on a constant +scale to + facilitate comparison. + +For controlled precision modes printer output is: + + N h k l 2q Nscans Natt b1 Peak b2 Inet s(Inet), +where + Nscans is the number of scans done, + Inet is the net count, including attenuation and +normalized + to 1 scan. + + There are also other messages which will appear only if +there are angle setting or scan collisions, or problems with +timing. The routine should be able to detect these and continue +its normal sequence. + + + Profile Analysis During Data Collection + + Profile analysis, if requested, is only done for peaks with +Inet > 2*s(Inet), based on minimum background measurements from +TP (usually 0.1 of the scan time). Profiles are taken at 0.01ø +steps of the scan and the analysis is done on a smoothed profile +to minimize random statistical fluctuations. If the number of +the intensity weighted maximum smoothed profile point (MaxI) is +more than a movement tolerance away from the number of the +calculated a1 point (MaxA) and Inet > 5*s(Inet) then the +following appears on the printer + + h k l MaxI MaxA b1 Peak b2 + +no profile analysis is done and the measurement is repeated once +more. If the same thing happens a second time, results with no +profile analysis are used. +This can occur for two reasons, + + 1. the reflection is weak and random statistics are the cause, + 2. the crystal has moved and most measurements show this error. +In this case + the crystal should be reoriented. + + The movement tolerance value is based on the scan width +parameters and is + + TOL = 100*(As + Cs)/8 where + + 100 is the number of profile points/deg. of scan, + As is the angular scan width before a1, and + Cs is the angular scan width after a2. + + Thus if As = Cs = 1, the tolerance is 0.25ø or 25 profile +points. This can be augmented by 20, 10 or 5 points with the SW +command using switches 6, 7 and 8, to give a maximum of 35 extra +points, i.e. 0.35ø of scan. + + The profile display is useful for monitoring the stability +of the crystal, both for mechanical movement and deterioration. + + Profiles may be saved in compressed form on the binary file +PROFL7.DAT by setting switch 9. This file will tend to become +rather large and normally this option is not selected. Records +in the PROFL7.DAT file are 128 bytes long (32 4 byte variables). +Variables are 4 bytes except for profile points which are 2 +bytes. + +For each reflection the records are as follows + +Record 1 h,k,l, Npts, Ilow, Ihigh, Frac, Ib1, Icount, Ib2, 44 +profile pts, + where + Npts is the number of profile points (+ 1000*Nstd if +reference reflection), + Ilow is the profile point number at low angle cutoff (1 if +no analysis) + Ihigh is the profile point number at high angle cutoff (Npts +if no analysis) + Frac is the ratio 1 bkgd time/peak time (usually 0.1 if no +analysis) + Ib1 is the low angle background for time Frac + Icount is the total count for all points + Ib2 is the high angle background for time Frac + Ipts are 44 profile points, as Value 32000. + +Records 2 to Nrecs 64 profile points, where + Nrecs is (Npts + 20 + 63)/64 + +PROFL7.DAT can be transformed into an ASCII file with the command +AP. The file produced has the default name of PROFL7.ASC and the +following format for each reflection + h,k,l, Npts, Ilow, Ihigh, Frac, Ib1, Icount, Ib2 + ( 3I4, 3I5, F8.5, I6, I7, I6) + (Npts + 9)/10 lines of up to 10 profile points (10I6). + + + Intensity Data on the IDATA.DA file + + Intensity data is written to the file IDATA.DA, starting at +record 20 in the following format. + + 10 reflections per record as + 10 values of 1000*(h + 500) + k + 500 + " " " 1000*(l + 500) + Ia (attenuator #) + " " " Low angle background (after any profile +analysis) + " " " Peak count (after any profile +analysis) + " " " High angle background (after any profile +analysis) + " " " 10*speed + background time fraction + " " " Reflection sequence # + " " " y (999 if reference reflection) + + The intensity data on the direct access IDATA.DA file can be +also converted, with the command AI, into a formatted ASCII file +suitable for transmission to, or processing by, other systems. + + The contents and format of the ASCII file are : + h,k,l, Ia, Ib1, Ipeak, Ib2, Time, Nref, Ipsi + ( 3I4, I2, I6, I7, I6, F9.5, I6, I5), where + Ia is the attenuator index (0 to 5), + Ib1 is the low angle background, + Ipeak is the total peak count, + Ib2 is the high angle background, + Time is (time for 1 background) / (Time for peak), i.e. + FRAC for normal scans, or + 10*number of scans + FRAC for controlled precision +modes, + Nref is the reflection sequence number, + Ipsi is the y value, usually 0, 999 for standards. + +Example: + Command go + Start Data Collection (Y) ? + Type the space group symbol P 41 + Do you wish to change the order of data collection (N) ? + Start at Reflection 1, Segment 1, Set 1, Record 20 (Y) ? + Measure the Translation element absences (Y) ? + Is everything OK (Y) ? + + +K Kill operation at the end of the current reflection + + During lengthy operations it is essential to have some means +of interrupting the procedure. This is achieved by making the +routine recognize unsolicited keyboard input at critical points +during execution. If the K key is struck during AL, GO or IE for +example, the program sequence will be interrupted at the end of +the operation on the current reflection and control returned to +the keyboard monitor. + + +Q Quit after the next set of reference reflections + + As for K, but the return to the keyboard monitor is after +the next set of reference reflections during the GO command. + + For both K and Q, information is saved to allow the +interrupted operations (GO or AL) to be resumed automatically if +no changes are made to the control parameters for the operation. + + +LR Last Reflection written to IDATA.DA + + Each time a record of 10 reflections is written to IDATA.DA, +the current reflection, set and segment numbers and record number +are written to record 10. This information can be recovered with +LR. + + Restarting Data Collection after a Crash + + Occasionally, due to a machine or power failure it is +necessary to restart data collection completely from scratch. At +such times the information for a restart has not been saved and +it is necessary to recover it from the printout and IDATA.DA +file. + + The important things to know about restarting are : + + h,k,l of the first refln to be collected, + the set and segment numbers of that reflection, + the record number in the IDATA.DA file where the new data +is to start, + the number of the first reflection, though this is not +essential. + + It is safest to always have the reference reflection +printing turned on (SW5=1), as it shows the next h,k,l, +reflection number, set number, segment number, and record number +before each set of reference measurements. The set and segment +numbers are also printed at the start of each segment. + + To restart the collection there are three choices. + + a. Restart at the last set of standards, which is simple but a +bit wasteful. + + b. Use PD/1 to search for the last valid intensity record + written. As explained above, data is written 10 reflections + per record, therefore assuming reference measurements were + taken after every 100 reflections at the most 10 records + will need to be printed to find how far the data collection + had progressed beyond the last set of reference reflections. + The h,k,l sequence can be followed down the records until + there is a discontinuity between 2 records. This happens + because the same file is used for all data collections, and + data from previous collections are probably on the file. + This means that data up to record n on the file is for the + present crystal, but the data in record n+1 is from another + crystal. The last reflection in record n is the last + reflection saved together with its reflection number. Using + this information and the set and segment numbers from the + last reference reflection print, the restart is at + + Next h,k,l, reflection-number+1, set and segment numbers, +record n+1 + + c. Use the LR command to find the required information which is + written each time a record of intensity data is written, + i.e. every 10 reflections. ++ +
+
+GS Grid Search measurement in 2q/w/c + + The intensity of a single reflection or a region of +reciprocal space can be measured in small steps on an angular +grid and output to the printer as a field of numbers. This can +be very useful in trying to deal with poor or split crystals, +before data collection is started. + +Example: + Command gs + Sample an Angular Grid (Y) ? + Type the grid specs. + A response of+ +is interpreted as no variation of that axis. + Type start, end & step for 2THETA 16.2,18.0,.2 + Type start, end & step for OMEGA .5,.4,.1 + Type start, end & step for CHI + Counting time per step (1 sec) + + 2THETA ACROSS page, from 16.200 in 10 steps, to 18.000 + OMEGA DOWN page, from 359.500 in 10 steps, to 0.400 + + 17 5 7 12 22 14 18 9 8 10 + 15 11 11 16 25 25 21 13 15 15 + 13 11 10 23 20 22 43 20 13 13 + 11 13 16 26 44 165 1179 327 44 20 + 16 15 17 53 153 1309 1809 985 111 56 + 13 17 31 1881 405 1945 1140 249 58 36 + 11 23 57 1005 1837 1048 257 73 32 23 + 3 10 15 65 584 209 49 34 12 11 + 14 8 11 13 34 28 29 21 11 12 + 10 10 13 11 20 17 14 16 16 12 + + +IE Intensity measurement for Equivalent reflections + +Prerequisites: LA PS SD (SG) TM TP and a valid Matrix + + Similar to IR, but as the reflections are typed in, all +equivalent h,k,l values other than Friedel equivalents, are added +to the list and subsequently each one is measured using the +current measurement parameters. This command is particularly +useful for checking Laue group symmetry before data collection is +started, and also to examine the reflection profile shape in +different directions. + +Example: + Command ie + Intensity Measurements for Equivalent Reflections (Y) ? + Type the space group symbol (P 1) p 41 + Type h,k,l for up to 50 reflections. CR = End. + Next h,k,l (End) 1,2,3 + 1 2 3 2 1 3 1 2 3 2 1 3 + Next h,k,l (End) + + Output is as for IR below. + + +IM Intensity Measurement of the reflection which is in the +detector + +Prerequisites: SD TP + + Occasionally during initial set up it is useful to measure +the reflection which is set, without knowing its indices. This +command does this using the current measurement conditions, +except that no y rotation is possible. Values of h,k,l are +requested, but are only used as a label. Again, output is as for +IR below. + + +IP Intensity measurement in Psi steps for empirical absorption + +Prerequisites: LA SD TM TP and a valid Matrix + + This is a command with the specific purpose of writing a +file (CURVES.DAT) of intensity measurements for a set of +reflections, each of which is measured 37 times in 10ø steps of y +from 0ø to 360ø. The same restrictions on y apply as for A8 with +Kappa geometry goniometers, i.e. only reflections with c in the +range 80ø to 100ø may be used, and these can be found with BC. +For Euler geometry goniometers, there are mechanical restrictions +as c approaches 0ø, but they are much less severe. + +The contents and format of the CURVES.DAT file is + +Lines 1 to 3 Orientation matrix (3(1X,3F10.6/)) +Lines 4 to 40 37 lines of data for 1st reflection in 10ø y +steps + h,k,l, 2q, w, c, f, y, Inet (3I4,5F8.2,I8) +Lines 41 to 77 Same for 2nd reflection etc. + +Example: + Command ip + Collect Psi scan data + Do you want to write data to CURVES.DAT (Y) ? + Type h,k,l for up to 50 reflections. CR = End. + Next h,k,l (End) 1,2,3 + Next h,k,l (End) + + +IR Intensity measurement for specifed Reflections + +Prerequisites: LA PS SD (SG) TM TP and a valid Matrix + + Reflections from a list of up to 100 sets of h,k,l values +can be measured according to the current measurement parameters. +If a range of y values has been specified with PS, each +reflection is measured as many times as possible over that range. +Reflections which are considered to be systematic absences +according to the space group specified in SG can be measured or +not, at the user's discretion. If no space group has been given +it is asked for. + + Output is h,k,l, 2q, Frac, Natt, B1, Peak, B2, y, Inet + +where Frac is (Time for 1 background / Time for peak), + B1, B2 are the backgrounds after profile analysis, + Inet is the net count after profile analysis. + +Example: + Command ir + Intensity Measurements for Individual Reflections + Type h,k,l and +/ 2Theta sense (+) for up to 50 reflections CR += End + Next h,k,l (End) 1 1 12 + Next h,k,l (End) + + 1 1 12 24.58 .345 0 51 2891 51 .00 2740 + + +LP Line Profile plot on the printer + + This command performs a step scan of a specified reflection, +for a specified number of steps of given size, for a given angle +and produces a normalized plot on the printer. This should not +be confused with the normal terminal profile display which uses +the current measurement conditions. + +Example: + Command lp + Plot a Line Profile on the Printer (Y) ? + Scan type: Theta/2Theta or Omega, 0 or 1 + Type the no. of pts before & after the peak, 500 max. 10,10 + Type the step size in deg. and the count time/step in secs .1,1 + + +SA Set All angles to specified values + + This command provides a means of setting the instrument to +specified angles which are not necessarily those for a +reflection. + + +SC Set c to the specified value + +SO Set w to the specified value + + +SP Set f to the specified value + + +SR Set Reflection: h,k,l, + +Prerequisites: LA SD (SG) TM TP and a valid Matrix + + The reflection specified is set at the y value requested +(default 0ø), provided it is within the current limits set by TM +and is not a systematic absence according to the space group +specified in SG. Fractional values of h,k,l are allowed. + + +ST Set 2q to the specified value + +TC Timed Counts + + This is the command for taking either + a. a single stationary timed count with a given attenuator; or + b. a series of such counts to check the stability of the x ray + generator and counting system. + + The command asks for the option to be used and then the +count time in seconds and an attenuator index (default 0). + + If the second option is chosen an initial count of 100 times +the input time is taken in order to establish a reliable mean +count, then counts are taken repeatedly for the input time and +printed, 10 per line, as the deviation from the mean together +with one of the following + blank if the deviation is within 1 s of the +mean count, or + A if between 1 and 2 s, + B if between 2 and 3 s and + C if more than 3 s. +At the end of 50 such lines (500 counts), a summary is printed +showing the observed and theoretical distribution of deviations. +This process will continue until stopped by the K command. + +Example: + Command tc + Timed Count at a Point (Y) ? + Type the Count Time in seconds 1 + Do you wish to repeat the counting for a stability test (Y) ? n + Time 1.000, Count 115909. + Do you want to repeat the procedure (N) ? + + When repeated counting is done, output similar to the +following will appear on the printer. + + A count is taken for 50.00 secs to establish a reasonable +mean. Counts are then repeated 500 times and a statistical +summary printed. + +Time 0.50, Mean Count 12429. Sigma(Mean) 111.5 +The deviations from the Mean Count are printed followed by A, B +or C, if the +deviation is more than 1, 2 or 3 Sigma(Mean). + + 101 4 27 113A 75 79 15 40 43 110 + ................................................ + ................................................ + 125A 86 154A 63 222A 20 75 109 30 73 + + Distribution of Counts Observed Theoretical + .GT. 0.674*Sigma 49.2% 50.0% + .GT. 1.000*Sigma 30.0% 31.7% + .GT. 2.000*Sigma 5.0% 4.6% + .GT. 3.000*Sigma 0.4% 0.3% + + +ZE ZEro the instrument angles + + This command sets all angles to 0ø or initiates a seek of +zero marking switches. The order and timing of axis movement +depends on the particular goniometer. +
+
+ The mechanical setup required to take photographs will +depend on the particular diffractometer in use. The photograph +commands merely provide a means of turning the crystal to the +required orientation. + + +PL Photograph in the Laue mode + +Prerequisite: Valid Matrix + + A specified direction h,k,l is set along the direct beam and +the shutter opened for a specified time with no circles moving +during exposure. It is not very useful to attempt to take a Laue +photo on machines with a monochromator. + +Example: + Command pl + Set for a Laue Pattern along a given row (Y) ? + Type the indices of the row 1,2,3 + The setting is NOT feasible + Command pl + Set for a Laue Pattern along a given row (Y) ? + Type the indices of the row 3,2,1 + Setting angles for row 3 2 1 0.000 15.501 90.000 +123.690 + Set it (Y) ? + + +PO Photograph in the Oscillation mode + + A specified real cell direction is set vertically and w is +rotated through a given, usually small, range a specified number +of times. + +Example: + Command po + Oscillation Picture (Y) ? + Type the omega scan limits 5,5 + Type the time to perform 1 scan in minutes 1 + Type the number of repeats (1) 4 + + +PR Photograph in the Rotation mode + + A specified real cell direction is set vertically and w +rotated through a given, usually large, range once only. + +Example: + Command pr + Set a Direct Lattice Row upwards along the Omega Rotation Axis + Confirm (Y) + Type the indices of the row 0 1 0 + The Periodicity for a Primitive Lattice is 9.932 Angstroms + Type the Crystal to Film Distance in mm 200 + Separation in mm between the + and nth levels + + 1 28.6 + 2 57.7 + 3 87.7 + 4 119.2 + 5 152.9 + 6 189.7 + 7 230.9 + 8 278.5 + 9 335.6 + Setting angles .000 .000 149.178 1.430 ++ +
+
+AH Angles to H, k, l + + The h, k, l values associated with a set of Euler angles are +calculated and printed as fractional values. + +Example: + Command ah + Calculate Reciprocal Coordinates + Type the reflection angles (End) 12,0,50,45 + Reciprocal Coordinates (h,k,l) 1.340 1.340 2.258 + Type the reflection angles (End) + + +AI Ascii Intensity data file conversion + + Intensity data on the binary file IDATA.DA is converted to +ASCII and written to a file, which has the default name +IDATA.ASC, in the format described under GO. + + +AP Ascii Profile data file conversion + + The profile data on the binary file PROFL7.DAT is converted +to ASCII and written to a file, which has the default name +PROFL7.ASC, in the format described under GO. + + +BC Big c search for y rotation + + Prerequisites : SG TM Valid matrix + + When measuring intensities with y rotation, the range of +permissible y values increases with c, until at c = +/ 90ø a +complete 360ø y rotation is always possible. On Euler geometry +machines the restriction on the y range comes about because w +moves from the bisecting position by a maximum of +/ |90 cb|, +where cb is the c value at the bisecting position. If cb is near +0ø the w excursion will approach 90ø and collisions will occur as +the c ring approaches the tube mounting. For reflections where +cb approaches 90ø the w excursion is a minimum and usually the +full 360ø rotation is attainable. On kappa geometry machines +similar restrictions apply, but a more severe restriction occurs +because of the small range of c attainable above c = 90ø. This +range is 2a 90ø and as a is usually around 50ø only reflections +with cb in the range 80ø to 90ø can have full 360ø y rotation. +The BC command will find all reflections with 2q less than a +specified maximum and cb between a specified minimum, usually +80ø, and 90ø. + +Example: + Search for reflections with High Chi Values + + Type the minimum acceptable chi value (80) + Type 2theta(max) (100.0) 30 + h,k,l for 2theta 30.000, chi 90 8.525 2.635 1.466 + Reflections with chi greater than 80.000 + h k l 2theta omega chi phi + 3 1 1 7.294 .000 82.829 355.234 + 3 1 0 6.988 .000 81.821 197.964 + 5 1 1 11.270 .000 82.603 82.854 + 6 2 2 14.617 .000 82.829 355.234 + 6 2 1 14.186 .000 88.445 264.275 + 6 2 0 14.001 .000 81.821 197.964 + 8 2 1 18.199 .000 85.679 124.069 + 8 2 0 18.040 .000 81.139 161.016 + 7 3 2 17.703 .000 81.733 308.986 + 7 3 1 17.339 .000 82.627 263.346 + 8 2 2 18.554 .000 84.587 51.404 + + +BI Big Intensity search in the IDATA.DA file + + When a data collection is complete, it is normal to use the +more intense higher angle reflections to collect accurate data +for cell determination with AL and MM or LC. This command +searches the intensity data file for the 25 biggest intensities +in the range of IDATA.DA records given, with 2q values greater +than a minimum. It is only necessary to search the IDATA records +containing the unique set, as AL will expand the unique h,k,l +values. + +Example: + Command bi + Search for the 25 biggest Inet/Sigma(Inet) (Y) ? + Type 2thetamin 25 + Intensity data is in records 20 to 154 + Type the first and last record numbers (All) 20 100 + Do you want to search more records (N) ? + +The following output appears on the printer + + h k l 2Theta Inet I/SigI + 5 1 2 25.60 72050 268.41 + 5 4 2 31.37 58198 241.21 + ................................. + ................................. + 2 1 5 33.96 25302 159.05 + +HA H, k, l to Angles + + The Euler angles for specified h,k,l and y values are +calculated and printed, in the order 2q, w, c, f, y. Fractional +indices are allowed. + +Example: + Command ha + Type h, k, l, Psi (End) 1,2,3 + 1 2 3 15.251 0.000 53.301 63.435 0.000 + Type h, k, l, Psi (End) + + +IN INitialize integer parts of angles. + + This command is meant for initializing the integer parts of +the current angle values, for instruments that do not have +absolute encoding systems. It will not be applicable to most +systems. + + +NR set the NRc program flag + + As explained on page 12, there is a flag called NRC which +can be set to take care of the definition of the c zero position. +If c = 0 occurs when the f circle mechanism is at the bottom of +the c circle NRC should be set to 1, otherwise 1. + + +P9 rotate f by 90ø + + This command is meant to help with optical centring during +the initial crystal setup. Usually, the f circle must be rotated +several times during this process and this command helps with +this by rotating f so that successive 90ø rotations bring both +goniometer head translations into a position normal to the +viewing direction so that they may be adjusted. + + +PA Print Angle settings + + The present Euler angles at which the circles are set are +printed on the terminal in the order 2q, w, c, f. + + The h,k,l values printed are the last values used and may +not correspond to the angles printed. + +Example: + Command pa + Current values are 1 2 3 15.251 0.000 53.301 0.000 + + +PD Print Data of all forms + + All forms of data, basic and intensity, may be printed, +either on the terminal or to hard copy. If intensity data is +being printed, it is advisable to print only selected small +quantities of data, or printing time can become very lengthy. + +Example: + Command pd + Print Data on Terminal or LPT + Options are : 0 Print Basic Data on Terminal + 1 Print Basic Data on LPT + 2 Print Intensity Data on Terminal + 3 Print Intensity Data on LPT + Type your choice (0) 0 + + Space group P 2/M Wavelength 0.70932 + Orientation Matrix Theta +Matrix + 0.09999949 0.00000003 0.00387554 0.00503130 0.00196553 +0.00155299 + 0.00000000 0.06250248 0.00000001 0.00000000 0.00038998 +0.00000000 + 0.00000000 0.00000000 0.05542216 + Cell 10.0245 15.9994 18.0433 90.000 94.000 +90.000 + D2theta 0.000 Domega 0.000 Dchi 0.000 + No attenuators. + No Psi rotation + 1 Reference reflections every 100 reflections + 4 0 0 + No Re orientation during data collection. + 16 Alignment/Re orientation Reflections (including Friedel +equivalents) + 1 2 3 2 1 3 1 2 3 2 1 3 + 3 2 1 2 3 1 3 2 1 2 3 1 + + Type+when ready to proceed. + + 2Theta Limits: Min 4.000; Max 50.000. Hmax 12, Kmax 20, +Lmax 22. + There are NO Explicit Absence Conditions + Omega/2Theta Scan. Profile analysis. + Bisecting Geometry. Scan speed 4.000deg/min + Scan Parameters: 1.000 + 0.700*tan(theta) + 1.000 + Time/Precision Params: Bkfrac 0.100; Tmax 10.0, PA 1.00, +PM 1.00 + Segment Data (DH Matrices) 2 segment(s) + 0 0 0 1 0 0 0 1 0 0 0 1 + 1 0 1 1 0 0 0 1 0 0 0 1 + Next reflection: 0 0 0, # 1, set 1, segment 1, at +record 20 + + For intensity data each line contains the following : + +N h k l 2q Frac Natt Blow Peak Bhigh y Inet Inet/s(Inet) + +most of which is self explanatory but, + N is blank or the reference reflection number. + Frac is 10*scan speed + time ratio for normal scans, or + 10*number of scans + time ratio for precision +scans. + Time ratio is the background time/peak time. + Background time is the time for 1 background, and + peak time is the scan time, after profile analysis. + Natt The attenuator number (0 to 5) + Blow Low angle background + Peak Integrated peak count + Bhigh High angle background. + If there is profile analysis, both backgrounds and +the peak count + are adjusted to reflect the cut off points, and the +time ratio is + that for the adjusted values. + y The value for the measurement, usually 0ø. 999 +for standards. + Inet Net intensity, with profile analysis, if used. + +Example: + Command pd + Print Data on Terminal or LPT + Options are : 0 Print Basic Data on Terminal + 1 Print Basic Data on LPT + 2 Print Intensity Data on Terminal + 3 Print Intensity Data on LPT + Type your choice (0) 2 + + Attenuator(0) 1.00 + Attenuator(1) 18.14 + + Type 2thetamin, 2thetamax and min(I/sigI) (All Reflns) + Type the first and last record numbers (All) 31 + + 12 7 0 61.639 40.250 0 123. 451. 123. .000 +447 21.05 + 11 7 0 57.435 40.525 0 204. 1627. 204. .000 +1621 40.19 + 10 7 0 53.416 40.250 0 124. 480. 124. .000 +476 21.73 + 9 7 0 49.591 40.250 0 135. 524. 135. .000 +520 22.72 + 8 7 0 45.975 40.250 0 155. 668. 155. .000 +664 25.69 + 1 10 0 0 43.527 40.264 0 402. 39627. 402. +35607 145.70 + 2 0 0 5 31.778 40.218 0 256. 35154. 256. +32594 148.84 + 3 0 10 0 42.556 40.243 0 396. 41735. 396. +37775 152.28 + 7 7 0 42.590 40.446 0 248. 1564. 248. .000 +1557 39.37 + 8 8 0 49.045 40.667 0 472. 10935. 472. .000 +10923 104.46 + + Do you want to print more records (N) ? + + +RB Read the Basic data from the IDATA.DA file + + All the current control parameters for all commands, plus +all derived quantities such as the orientation matrix, h,k,l +limits etc are written in the first 3 records of the IDATA.DA +file. The RB command reads these values, which are written by +the WB command or whenever a data collection is started with the +GO command. (See the description of the IDATA file) + +UM (UMpty) Count the unique reflections within the 2q limits + (Umpty a large but indefinite number O.E.D.) + + An accurate count of the unique reflections within the 2q +limits for the unique DH segments derived with SG is calculated. +From this users can estimate (allowing for reference reflections, +scan time, slewing time and any re orienation), how long it will +take to collect a unique set. + +Example: + Command um + Count the number of reflections in each segment (Y) + DH Segment 1 contains 1718 reflections + DH Segment 2 contains 1416 reflections + + +VM set the circles to the View Microscope position + + The Euler angles for the most convenient microscope viewing +position are stored in the goniom.ini file and used by the VM +command to set the instrument to this position ready for optical +centring of a crystal, in conjunction with the P9 command. + + +WB Write the Basic data to the IDATA.DA file + + Write all the current parameters to the first 3 records of +the IDATA file. It is a good idea to use this command whenever a +valid orientation matrix is established, as this will save +trouble on subsequent restarts planned or not! + +
+ + \ No newline at end of file diff --git a/doc/user/tricsingle.htm b/doc/user/tricsingle.htm index cacaede3..15fa387b 100644 --- a/doc/user/tricsingle.htm +++ b/doc/user/tricsingle.htm @@ -14,14 +14,20 @@ to be solved are:
The DIFRAC commands are accessed by prepending the difrac commands with dif. For example: "dif td" calls the difrac td command. For more information on DIFRAC commands see the separate -DIFRAC manual. +DIFRAC manual.
Run Number | $run |
---|---|
Title | $tit |
User | $user |
Sample | $sample |
wavelength | $lam |
Status | $stat |
Scan Variables | $svar |
File | $fil |
Last Scan Command | $lscan |
Run Number | $run |
---|---|
Title | $tit |
User | $user |
Sample | $sample |
wavelength | $lam |
Sample Temperature | $tem |
Status | $stat |