################################ Diffcalc User Guide (You Engine) ################################ .. rubric:: Diffcalc: A diffraction condition calculator for diffractometer control :Author: Rob Walton :Contact: rob.walton (at) diamond (dot) ac (dot) uk :Website: https://github.com/DiamondLightSource/diffcalc .. toctree:: :maxdepth: 2 :numbered: See also the `quickstart guide at github `_ Introduction ============ This manual assumes that you are running Diffcalc within OpenGDA or have started it using IPython. It assumes that Diffcalc has been configured for the six circle diffractometer pictured here: .. figure:: youmanual_images/4s_2d_diffractometer.png :scale: 20 :align: center 4s + 2d six-circle diffractometer, from H.You (1999) Your Diffcalc configuration may have been customised for the geometry of your diffractometer and possibly the types of experiment you perform. For example, a five-circle diffractometer might be missing the nu circle above. The laboratory frame is shown above. With all settings at zero as shown the crystal cartesian frame aligns with the laboratory frame. Therefor a cubic crystal mounted squarely in a way that the U matrix (defined below) is unitary will have h||a||x, k||b||y & l||c||z, crystal and reciprocal-lattice coordinate frames are defined with respect to the beam and to gravity to be (for a cubic crystal): Overview ======== The following assumes that the diffractometer has been properly leveled, aligned with the beam and zeroed. See the `SPEC fourc manual `__. Before moving in hkl space you must calculate a UB matrix by specifying the crystal's lattice parameters (which define the B matrix) and finding two reflections (from which the U matrix defining any mismount can be inferred); and, optionally for surface-diffraction experiments, determine how the surface of the crystal is oriented with respect to the phi axis. Once a UB matrix has been calculated, the diffractometer may be driven in hkl coordinates. A valid diffractometer setting maps easily into a single hkl value. However for a diffractometer with more than three circles there are excess degrees of freedom when calculating a diffractometer setting from an hkl value. Diffcalc provides modes for using up the excess degrees of freedom. Diffcalc does not perform scans directly. Instead, Scannables that use diffcalc to map between reciprocal lattice space and real diffractometer settings are scanned using the Gda's (or minigda's) generic scan mechanism. Theory ------ Thanks to Elias Vlieg for sharing his dos based ``DIF`` software that Diffcalc has borrowed heavily from. The version of Diffcalc described here is based on papers by pHH. You. [You1999]_ and Busing & Levy [Busing1967]_. (See also the THANKS.txt file.) Getting Help ============ There are few commands to remember. If a command is called without arguments in some cases Diffcalc will prompt for arguments and provide sensible defaults which can be chosen by pressing enter. **Orientation**. The ``helpub`` command lists all commands related with crystal orientation and the reference vector (often used with surfaces). See the `Orientation Commands`_ section at the end of this manual:: >>> help ub ... **HKL movement**. The ``help hkl`` list all commands related to moving in reciprocal-lattice space. See the `Motion Commands`_ section at the end of this manual:: >>> help hkl ... Call help on any command. e.g.:: >>> help loadub loadub (diffcalc command): loadub 'name' | num -- load an existing ub calculation Diffcalc's Scannables ===================== To list and show the current positions of your beamline's scannables use ``pos`` with no arguments:: >>> pos Results in: **Energy and wavelength scannables**:: energy 12.3984 wl: 1.0000 **Diffractometer scannables**, as a group and in component axes (in the real GDA these have limits):: sixc: mu: 0.0000 delta: 0.0000 gamma: 0.0000 omega: 0.0000 chi: 0.0000 phi: 0.0000 mu: 0.0000 chi: 0.0000 delta: 0.0000 gamma: 0.0000 omega: 0.0000 phi: 0.0000 **Dummy counter**, which in this example simply counts at 1hit/s:: ct: 0.0000 **Hkl scannable**, as a group and in component:: hkl: Error: No UB matrix h: Error: No UB matrix k: Error: No UB matrix l: Error: No UB matrix **Parameter scannables**, used in some modes, these provide a scannable alternative to the `Motion`_ section. Some constrain of these constrain virtual angles:: alpha: --- beta: --- naz: --- psi: --- qaz: --- and some constrain physical angles:: phi_con: --- chi_con: --- delta_con:--- eta_con: --- gam_con: --- mu_con: --- Crystal orientation =================== Before moving in hkl space you must calculate a UB matrix by specifying the crystal's lattice parameters (which define the B matrix) and finding two reflections (from which the U matrix can be inferred); and, optionally for surface-diffraction experiments, determine how the surface of the crystal is oriented with respect to the phi axis. Start a new UB calculation -------------------------- A *UB calculation* contains the description of the crystal-under-test, any saved reflections, reference angle direction, and a B & UB matrix pair if they have been calculated or manually specified. Starting a new UB calculation will clear all of these. Before starting a UB-calculation, the ``ub`` command used to summarise the state of the current UB-calculation, will reflect that no UB-calculation has been started:: >>> ub <<< No UB calculation started >>> A new UB-calculation calculation may be started and lattice specified explicitly:: >>> newub 'example' >>> setlat '1Acube' 1 1 1 90 90 90 or interactively:: >>> newub calculation name: example crystal name: 1Acube a [1]: 1 b [1]: 1 c [1]: 1 alpha [90]: 90 beta [90]: 90 gamma [90]: 90 where a,b and c are the lengths of the three unit cell basis vectors in Angstroms, and alpha, beta and gamma are angles in Degrees. The ``ub`` command will show the state of the current UB-calculation (and the current energy for reference):: >>> ub UBCALC name: example n_phi: 0.00000 0.00000 1.00000 <- set CRYSTAL name: 1Acube a, b, c: 1.00000 1.00000 1.00000 90.00000 90.00000 90.00000 B matrix: 6.28319 0.00000 0.00000 0.00000 6.28319 0.00000 0.00000 0.00000 6.28319 UB MATRIX <<< none calculated >>> REFLECTIONS <<< none specified >>> CRYSTAL ORIENTATIONS <<< none specified >>> Load a UB calculation --------------------- To load the last used UB-calculation:: >>> lastub Loading ub calculation: 'mono-Si' To load a previous UB-calculation:: >>> listub UB calculations in: /Users/walton/.diffcalc/i16 0) mono-Si 15 Feb 2017 (22:32) 1) i16-32 13 Feb 2017 (18:32) >>> loadub 0 Generate a U matrix from two reflections ---------------------------------------- The normal way to calculate a U matrix is to find the position of **two** reflections with known hkl values. Diffcalc allows many reflections to be recorded but currently only uses the first two when calculating a UB matrix. Find U matrix from two reflections:: >>> pos wl 1 wl: 1.0000 >>> c2th [0 0 1] 59.99999999999999 >>> pos sixc [0 60 0 30 90 0] sixc: mu: 0.0000 delta: 60.0000 gam: 0.0000 eta: 30.0000 chi: 90.0000 phi: 0.0000 >>> addref [0 0 1] >>> pos sixc [0 90 0 45 45 90] sixc: mu: 0.0000 delta: 90.0000 gam: 0.0000 eta: 45.0000 chi: 45.0000 phi: 90.0000 >>> addref [0 1 1] Calculating UB matrix. Check that it looks good:: >>> checkub ENERGY H K L H_COMP K_COMP L_COMP TAG 1 12.3984 0.00 0.00 1.00 0.0000 0.0000 1.0000 2 12.3984 0.00 1.00 1.00 0.0000 1.0000 1.0000 Generate a U matrix from one reflection --------------------------------------- To estimate based on first reflection only:: >>> trialub resulting U angle: 0.00000 deg resulting U axis direction: [-1.00000, 0.00000, 0.00000] Recalculating UB matrix from the first reflection only. NOTE: A new UB matrix will not be automatically calculated when the orientation reflections are modified. Edit reflection list -------------------- Use ``showref`` to show the reflection list:: >>> showref ENERGY H K L MU DELTA GAM ETA CHI PHI TAG 1 12.398 0.00 0.00 1.00 0.0000 60.0000 0.0000 30.0000 90.0000 0.0000 2 12.398 0.00 1.00 1.00 0.0000 90.0000 0.0000 45.0000 45.0000 90.0000 Use ``swapref`` to swap reflections:: >>> swapref 1 2 Not calculating UB matrix as it has been manually set. Use 'calcub' to explicitly recalculate it. Recalculating UB matrix. Use ``delref`` to delete a reflection:: >>> delref 1 Generate a U matrix from two lattice directions ----------------------------------------------- Another approach to calculate a U matrix is to provide orientation of **two** crystal lattice directions in laboratory frame of reference using ``addorient`` command. The first lattice direction will be aligned along the specified in the laboratory frame. The second lattice direction will be used to set azimuthal orientation of the crystal in the plane perpendicular to the first lattice orientation. Diffcalc allows many lattice directions to be recorded but currently uses only the first two when calculating a UB matrix. Find U matrix from two lattice directions:: >>> addorient [0 0 1] [0 0 1] >>> addorient [1 0 0] [1 1 0] Calculating UB matrix. Calculate a UB matrix --------------------- Unless a U or UB matrix has been manually specified, a new UB matrix will be calculated after the second reflection has been found, or whenever one of the first two reflections is changed. Use the command ``calcub`` to force the UB matrix to be calculated from the first two reflections. In case of using lattice orientations instead of reflections, use command ``orientub`` to force the UB matrix to be calculated from the first two orientations. If you have misidentified a reflection used for the orientation the resulting UB matrix will be incorrect. Always use the ``checkub``command to check that the computed reflection indices agree with the estimated values:: >>> checkub ENERGY H K L H_COMP K_COMP L_COMP TAG 1 12.3984 0.00 1.00 1.00 0.0000 1.0000 1.0000 2 12.3984 0.00 0.00 1.00 0.0000 0.0000 1.0000 Calculate a U matrix from crystal mismount ------------------------------------------- U matrix can be defined from crystal mismount by using a rotation matrix calculated from a provided mismount angle and axis. ``setmiscut`` command defines new U matrix by setting it to a rotation matrix calculated from the specified angle and axis parameters. ``addmiscut`` command applies the calculated rotation matrix to the existing U matrix, i.e. adds extra mismount to the already existing one:: >>> setmiscut 5 [1 0 0] n_phi: -0.00000 -0.08716 0.99619 n_hkl: 0.00000 0.00000 1.00000 <- set normal: angle: 5.00000 axis: 1.00000 -0.00000 0.00000 Manually specify U matrix ------------------------- Set U matrix manually (pretending sample is squarely mounted):: >>> setu [[1 0 0] [0 1 0] [0 0 1]] Recalculating UB matrix. NOTE: A new UB matrix will not be automatically calculated when the orientation reflections are modified. Refining UB matrix from reflection ---------------------------------- UB matrix elements can be refined to match diffractometer settings and crystal orientation experimentally found for a given reflection with the corresponding reflection indices. ``refineub`` command rescales crystal unit cell dimensions to match with the found scattering angle value and recalculates mismount parameters to update U matrix:: >>> refineub [1 0 0] current pos[y]: y Unit cell scaling factor: 0.99699 Refined crystal lattice: a, b, c: 0.99699 0.99699 0.99699 90.00000 90.00000 90.00000 Update crystal settings?[y]: y Warning: the old UB calculation has been cleared. Use 'calcub' to recalculate with old reflections or 'orientub' to recalculate with old orientations. Miscut parameters: angle: 2.90000 axis: -0.00000 1.00000 -0.00000 Apply miscut parameters?[y]: y n_phi: 0.67043 -0.00000 0.74198 n_hkl: 0.00000 0.00000 1.00000 <- set normal: angle: 42.10000 axis: 0.00000 1.00000 0.00000 Set the reference vector ------------------------- When performing surface experiments the reference vector should be set normal to the surface. It can also be used to define other directions within the crystal with which we want to orient the incident or diffracted beam. By default the reference vector is set parallel to the phi axis. That is, along the z-axis of the phi coordinate frame. The `ub` command shows the current reference vector along with the orientation relative to the z-axis, at the top its report (or it can be shown by calling ``setnphi`` or ``setnhkl'`` with no args):: >>> ub ... n_phi: 0.00000 0.00000 1.00000 <- set n_hkl: -0.00000 0.00000 1.00000 normal: None ... The ``<- set`` label here indicates that the reference vector is set in the phi coordinate frame. In this case, therefore, its direction in the crystal's reciprocal lattice space is inferred from the UB matrix. To set the reference vector in the phi coordinate frame use:: >>> setnphi [0 0 1] ... This is useful if the surface normal has be found with a laser or by x-ray occlusion. This vector must currently be manually calculated from the sample angle settings required to level the surface (sigma and tau commands on the way). To set the reference vector in the crystal's reciprocal lattice space use (this is a quick way to determine the surface orientation if the surface is known to be cleaved cleanly along a known axis):: >>> setnhkl [0 0 1] ... Motion ====== Once a UB matrix has been calculated, the diffractometer may be driven in hkl coordinates. A given diffractometer setting maps easily into a single hkl value. However for a diffractometer with more than three circles there are excess degrees of freedom when calculating a diffractometer setting from an hkl value. Diffcalc provides many for using up the excess degrees of freedom. By default Diffcalc selects no mode. Constraining solutions for moving in hkl space ---------------------------------------------- To get help and see current constraints:: >>> help con ... >>> con DET REF SAMP ------ ------ ------ delta a_eq_b mu gam alpha eta qaz beta chi naz psi phi mu_is_gam ! 3 more constraints required Type 'help con' for instructions Three constraints can be given: zero or one from the DET and REF columns and the remainder from the SAMP column. Not all combinations are currently available. Use ``help con`` to see a summary if you run into troubles. To configure four-circle vertical scattering:: >>> con gam 0 mu 0 a_eq_b gam : 0.0000 a_eq_b mu : 0.0000 In the following the *scattering plane* is defined as the plane including the scattering vector, or momentum transfer vector, and the incident beam. **DETECTOR COLUMN:** - **delta** - physical delta setting (vertical detector motion) *del=0 is equivalent to qaz=0* - **gam** - physical gamma setting (horizontal detector motion) *gam=0 is equivalent to qaz=90* - **qaz** - azimuthal rotation of scattering vector (about the beam, from horizontal) - **naz** - azimuthal rotation of reference vector (about the beam, from horizontal) **REFERENCE COLUMN:** - **alpha** - incident angle to surface (if reference is normal to surface) - **beta** - exit angle from surface (if reference is normal to surface) - **psi** - azimuthal rotation about scattering vector of reference vector (from scattering plane) - **a_eq_b** - bisecting mode with alpha=beta. *Equivalent to psi=90* **SAMPLE COLUMN:** - **mu, eta, chi & phi** - physical settings - **mu_is_gam** - force mu to follow gamma (results in a 5-circle geometry) Diffcalc will report two other (un-constrainable) virtual angles: - **theta** - half of 2theta, the angle through the diffracted beam bends - **tau** - longitude of reference vector from scattering vector (in scattering plane) Example constraint modes ------------------------ There is sometimes more than one way to get the same effect. **Vertical four-circle mode**:: >>> con gam 0 mu 0 a_eq_b # or equivalently: >>> con qaz 90 mu 0 a_eq_b >>> con alpha 1 # replaces a_eq_b **Horizontal four-circle mode**:: >>> con del 0 eta 0 alpha 1 # or equivalently: >>> con qaz 0 mu 0 alpha 1 **Surface vertical mode**:: >>> con naz 90 mu 0 alpha 1 **Surface horizontal mode**:: >>> con naz 0 eta 0 alpha 1 **Z-axis mode (surface horizontal)**:: >>> con chi (-sigma) phi (-tau) alpha 1 where sigma and tau are the offsets required in chi and phi to bring the surface normal parallel to eta. Alpha will determine mu directly leaving eta to orient the planes. Or:: >>> con naz 0 phi 0 alpha 1 # or any another sample angle **Z-axis mode (surface vertical)**:: >>> con naz 0 phi 0 alpha 1 # or any another sample angle Changing constrained values --------------------------- Once constraints are chosen constrained values may be changed directly:: >>> con mu 10 gam : 0.0000 a_eq_b mu : 10.0000 or via the associated scannable:: >>> pos mu_con 10 mu_con: 10.00000 Configuring limits and cuts --------------------------- Diffcalc maintains its own limits on axes. These limits will be used when choosing solutions. If more than one detector solution is exists Diffcalc will ask you to reduce the the limits until there is only one. However if more than one solution for the sample settings is available it will choose one base on heuristics. Use the ``hardware`` command to see the current limits and cuts:: >>> hardware mu (cut: -180.0) delta (cut: -180.0) gam (cut: -180.0) eta (cut: -180.0) chi (cut: -180.0) phi (cut: 0.0) Note: When auto sector/transforms are used, cuts are applied before checking limits. To set the limits:: >>> setmin delta -1 >>> setmax delta 145 To set a cut:: >>> setcut phi -180 This causes requests to move phi to be between the configured -180 and +360 degress above this. i.e. it might dive to -10 degrees rather than 350. Moving in hkl space ------------------- Configure a mode, e.g. four-circle vertical:: >>> con gam 0 mu 0 a_eq_b gam : 0.0000 a_eq_b mu : 0.0000 Simulate moving to a reflection:: >>> sim hkl [0 1 1] sixc would move to: mu : 0.0000 delta : 90.0000 gam : 0.0000 eta : 45.0000 chi : 45.0000 phi : 90.0000 alpha : 30.0000 beta : 30.0000 naz : 35.2644 psi : 90.0000 qaz : 90.0000 tau : 45.0000 theta : 45.0000 Move to reflection:: >>> pos hkl [0 1 1] hkl: h: 0.00000 k: 1.00000 l: 1.00000 >>> pos sixc sixc: mu: 0.0000 delta: 90.0000 gam: 0.0000 eta: 45.0000 chi: 45.0000 phi: 90.0000 Simulate moving to a location:: >>> pos sixc [0 60 0 30 90 0] sixc: mu: 0.0000 delta: 60.0000 gam: 0.0000 eta: 30.0000 chi: 90.0000 phi: 0.0000 Scanning in hkl space ===================== All scans described below use the same generic scanning mechanism provided by the GDA system or by minigda. Here are some examples. Fixed hkl scans --------------- In a 'fixed hkl scan' something (such as energy or Bin) is scanned, and at each step hkl is 'moved' to keep the sample and detector aligned. Also plonk the diffractometer scannable (sixc) on there with no destination to monitor what is actually happening and then throw on a detector (ct) with an exposure time if appropriate:: >>> #scan scannable_name start stop step [scannable_name [pos or time]].. >>> scan en 9 11 .5 hkl [1 0 0] sixc ct 1 >>> scan en 9 11 .5 hklverbose [1 0 0] sixc ct 1 >>> scan betain 4 5 .2 hkl [1 0 0] sixc ct 1 >>> scan alpha_par 0 10 2 hkl [1 0 0] sixc ct 1 Scanning hkl ------------ Hkl, or one component, may also be scanned directly:: >>> scan h .8 1.2 .1 hklverbose sixc ct 1 At each step, this will read the current hkl position, modify the h component and then move to the resulting vector. There is a danger that with this method k and l may drift. To get around this the start, stop and step values may also be specified as vectors. So for example:: >>> scan hkl [1 0 0] [1 .3 0] [1 0.1 0] ct1 is equivilant to:: >>> pos hkl [1 0 0] >>> scan k 0 .3 .1 ct1 but will not suffer from drifting. This method also allows scans along any direction in hkl space to be performed. Multidimension scans -------------------- Two and three dimensional scans:: >>> scan en 9 11 .5 h .9 1.1 .2 hklverbose sixc ct 1 >>> scan h 1 3 1 k 1 3 1 l 1 3 1 hkl ct 1 Commands ======== Orientation Commands -------------------- +-----------------------------+---------------------------------------------------+ | **STATE** | +-----------------------------+---------------------------------------------------+ | **-- newub** {'name'} | start a new ub calculation name | +-----------------------------+---------------------------------------------------+ | **-- loadub** 'name' | num | load an existing ub calculation | +-----------------------------+---------------------------------------------------+ | **-- lastub** | load the last used ub calculation | +-----------------------------+---------------------------------------------------+ | **-- listub** | list the ub calculations available to load | +-----------------------------+---------------------------------------------------+ | **-- rmub** 'name'|num | remove existing ub calculation | +-----------------------------+---------------------------------------------------+ | **-- saveubas** 'name' | save the ub calculation with a new name | +-----------------------------+---------------------------------------------------+ | **LATTICE** | +-----------------------------+---------------------------------------------------+ | **-- setlat** | interactively enter lattice parameters (Angstroms | | | and Deg) | +-----------------------------+---------------------------------------------------+ | **-- setlat** name a | assumes cubic | +-----------------------------+---------------------------------------------------+ | **-- setlat** name a b | assumes tetragonal | +-----------------------------+---------------------------------------------------+ | **-- setlat** name a b c | assumes ortho | +-----------------------------+---------------------------------------------------+ | **-- setlat** name a b c | assumes mon/hex with gam not equal to 90 | | gamma | | +-----------------------------+---------------------------------------------------+ | **-- setlat** name a b c | arbitrary | | alpha beta gamma | | +-----------------------------+---------------------------------------------------+ | **-- c2th** [h k l] | calculate two-theta angle for reflection | +-----------------------------+---------------------------------------------------+ | **-- hklangle** [h1 k1 l1] | calculate angle between [h1 k1 l1] and [h2 k2 l2] | | [h2 k2 l2] | crystal planes | +-----------------------------+---------------------------------------------------+ | **REFERENCE (SURFACE)** | +-----------------------------+---------------------------------------------------+ | **-- setnphi** {[x y z]} | sets or displays n_phi reference | +-----------------------------+---------------------------------------------------+ | **-- setnhkl** {[h k l]} | sets or displays n_hkl reference | +-----------------------------+---------------------------------------------------+ | **REFLECTIONS** | +-----------------------------+---------------------------------------------------+ | **-- showref** | shows full reflection list | +-----------------------------+---------------------------------------------------+ | **-- addref** | add reflection interactively | +-----------------------------+---------------------------------------------------+ | **-- addref** [h k l] | add reflection with current position and energy | | {'tag'} | | +-----------------------------+---------------------------------------------------+ | **-- addref** [h k l] (p1, | add arbitrary reflection | | .., pN) energy {'tag'} | | +-----------------------------+---------------------------------------------------+ | **-- editref** num | interactively edit a reflection | +-----------------------------+---------------------------------------------------+ | **-- delref** num | deletes a reflection (numbered from 1) | +-----------------------------+---------------------------------------------------+ | **-- clearref** | deletes all the reflections | +-----------------------------+---------------------------------------------------+ | **-- swapref** | swaps first two reflections used for calculating | | | U matrix | +-----------------------------+---------------------------------------------------+ | **-- swapref** num1 num2 | swaps two reflections (numbered from 1) | +-----------------------------+---------------------------------------------------+ | **CRYSTAL ORIENTATIONS** | +-----------------------------+---------------------------------------------------+ | **-- showorient** | shows full list of crystal orientations | +-----------------------------+---------------------------------------------------+ | **-- addorient** | add crystal orientation interactively | +-----------------------------+---------------------------------------------------+ | **-- addorient** [h k l] | add crystal orientation in laboratory frame | | [x y z] {'tag'} | | +-----------------------------+---------------------------------------------------+ | **-- editorient** num | interactively edit a crystal orientation | +-----------------------------+---------------------------------------------------+ | **-- delorient** num | deletes a crystal orientation (numbered from 1) | +-----------------------------+---------------------------------------------------+ | **-- clearorient** | deletes all the crystal orientations | +-----------------------------+---------------------------------------------------+ | **-- swaporient** | swaps first two crystal orientations used for | | | calculating U matrix | +-----------------------------+---------------------------------------------------+ | **-- swaporient** num1 num2 | swaps two crystal orientations (numbered from 1) | +-----------------------------+---------------------------------------------------+ | **UB MATRIX** | +-----------------------------+---------------------------------------------------+ | **-- checkub** | show calculated and entered hkl values for | | | reflections | +-----------------------------+---------------------------------------------------+ | **-- setu** | manually set u matrix | | {[[..][..][..]]} | | +-----------------------------+---------------------------------------------------+ | **-- setub** | manually set ub matrix | | {[[..][..][..]]} | | +-----------------------------+---------------------------------------------------+ | **-- calcub** | (re)calculate u matrix from ref1 and ref2 | +-----------------------------+---------------------------------------------------+ | **-- trialub** | (re)calculate u matrix from ref1 only (check | | | carefully) | +-----------------------------+---------------------------------------------------+ | **-- refineub** {[h k l]} | refine unit cell dimensions and U matrix to match | | {pos} | diffractometer angles for a given hkl value | +-----------------------------+---------------------------------------------------+ | **-- addmiscut** angle | apply miscut to U matrix using a specified miscut | | {[x y z]} | angle in degrees and a rotation axis | | | (default: [0 1 0]) | +-----------------------------+---------------------------------------------------+ | **-- setmiscut** angle | manually set U matrix using a specified miscut | | {[x y z]} | angle in degrees and a rotation axis | | | (default: [0 1 0]) | +-----------------------------+---------------------------------------------------+ Motion commands --------------- +-----------------------------+---------------------------------------------------+ | **CONSTRAINTS** | +-----------------------------+---------------------------------------------------+ | **-- con** | list available constraints and values | +-----------------------------+---------------------------------------------------+ | **-- con** {val} | constrains and optionally sets one constraint | +-----------------------------+---------------------------------------------------+ | **-- con** {val} | clears and then fully constrains | | {val} {val} | | +-----------------------------+---------------------------------------------------+ | **-- uncon** | remove constraint | +-----------------------------+---------------------------------------------------+ | **HKL** | +-----------------------------+---------------------------------------------------+ | **-- allhkl** [h k l] | print all hkl solutions ignoring limits | +-----------------------------+---------------------------------------------------+ | **HARDWARE** | +-----------------------------+---------------------------------------------------+ | **-- hardware** | show diffcalc limits and cuts | +-----------------------------+---------------------------------------------------+ | **-- setcut** {name {val}} | sets cut angle | +-----------------------------+---------------------------------------------------+ | **-- setmin** {axis {val}} | set lower limits used by auto sector code (None | | | to clear) | +-----------------------------+---------------------------------------------------+ | **-- setmax** {name {val}} | sets upper limits used by auto sector code (None | | | to clear) | +-----------------------------+---------------------------------------------------+ | **MOTION** | +-----------------------------+---------------------------------------------------+ | **-- sim** hkl scn | simulates moving scannable (not all) | +-----------------------------+---------------------------------------------------+ | **-- sixc** | show Eularian position | +-----------------------------+---------------------------------------------------+ | **-- pos** sixc [mu, delta, | move to Eularian position(None holds an axis | | gam, eta, chi, phi] | still) | +-----------------------------+---------------------------------------------------+ | **-- sim** sixc [mu, delta, | simulate move to Eulerian positionsixc | | gam, eta, chi, phi] | | +-----------------------------+---------------------------------------------------+ | **-- hkl** | show hkl position | +-----------------------------+---------------------------------------------------+ | **-- pos** hkl [h k l] | move to hkl position | +-----------------------------+---------------------------------------------------+ | **-- pos** {h | k | l} val | move h, k or l to val | +-----------------------------+---------------------------------------------------+ | **-- sim** hkl [h k l] | simulate move to hkl position | +-----------------------------+---------------------------------------------------+ Good luck --- RobW References ========== .. [You1999] H. You. *Angle calculations for a '4S+2D' six-circle diffractometer.* J. Appl. Cryst. (1999). **32**, 614-623. `(pdf link) `__. .. [Busing1967] W. R. Busing and H. A. Levy. *Angle calculations for 3- and 4-circle X-ray and neutron diffractometers.* Acta Cryst. (1967). **22**, 457-464. `(pdf link) `__.