Automation of invariom and of experimental charge density modelling of organic molecules with the preprocessor program InvariomTool

The program InvariomTool can be used to obtain high-quality X-ray structures of organic molecules by automating both invariom modelling and the modelling process employed in experimental charge density studies. InvariomTool is a preprocessor program for the XD package [Koritsánszky et al. (2003), Technical Report, Freie Universität Berlin] and allows the analysis of a structure in terms of the local atomic bonding environment in order to assign Hansen-Coppens pseudoatoms that are transferable from one molecule to another (invarioms). It relies on a database of invariom entries, each containing the invariom name, local atomic site symmetry, coordinate system, model-compound name and theoretically predicted multipole population parameters. The information on chemical equivalence and local atomic site symmetry determines which multipole parameters are to be refined in the least-squares procedure of an experimental charge density study. InvariomTool allows the user to generate input files either for invariom refinement, where parameters are fixed and taken from the database, or for an experimental refinement of multipole parameters.