update README

README.md

@@ -9,26 +9,29 @@ The actual scattering calculation is done by code developed by other parties.
 PMSCO wraps around that program and facilitates parameter handling, cluster building, structural optimization and parallel processing.
 In the current version, the [EDAC](http://garciadeabajos-group.icfo.es/widgets/edac/) code
 developed by F. J. García de Abajo, M. A. Van Hove, and C. S. Fadley (1999) is used for scattering calculations.
-Other code can be integrated as well.
+Instead of EDAC built-in routines, alternatively,
+the PHAGEN program from [MsSpec-1.0](https://msspec.cnrs.fr/index.html) can be used to calculate atomic scattering factors.
+
 
 Highlights
 ----------
 
-- angle or energy scanned XPD.
-- various scanning modes including energy, polar angle, azimuthal angle, analyser angle.
+- angle and energy scanned XPD.
+- various scanning modes including energy, manipulator angle (polar/azimuthal), emission angle.
 - averaging over multiple domains and emitters.
 - global optimization of multiple scans.
 - structural optimization algorithms: particle swarm optimization, grid search, gradient search.
 - calculation of the modulation function.
 - calculation of the weighted R-factor.
 - automatic parallel processing using OpenMPI.
+- tested on Linux cluster machines.
 
 
 Installation
 ============
 
-PMSCO is written in Python 3.6 and compatible with Python 2.7.
-The code will run in any recent Linux environment on a workstation or in a virtual machine.
+PMSCO is written in Python 3.6.
+The code will run in any recent Linux environment on a workstation or virtual machine.
 Scientific Linux, CentOS7, [Ubuntu](https://www.ubuntu.com/)
 and [Lubuntu](http://lubuntu.net/) (recommended for virtual machine) have been tested.
 For optimization jobs, a cluster with 20-50 available processor cores is recommended.
@@ -73,4 +76,17 @@ Copyright 2015-2020 by [Paul Scherrer Institut](http://www.psi.ch)
 Release Notes
 =============
 
+For a detailed list of changes, see the CHANGES.md file.
+
+2.2.0 (2020-09-04)
+------------------
+
+This release breaks existing project code unless the listed refactorings are applied.
+
+- Major refactoring: The 'symmetry' calculation level is renamed to 'domain'. 
+  The previous Domain class is renamed to ModelSpace, Params to CalculatorParams.
+  The refactorings must be applied to project code as well.
+- Included periodic table of elements with electron binding energies and scattering cross-sections.
+- Various bug fixes in cluster routines, data file handling, and in the PHAGEN interface.
+- Experimental sqlite3 database interface for optimization results.