Abstract: A general procedure is presented to derive force field parameters for molecules in the crystalline state on a case by case basis. The force filed parameters are fitted to accurate energies and forces generated by means of a hybrid method that combines DFT calculations with an empirical van der Waals correction. The mathematical structure of the force field, the generation of reference data, the choice of the figure of merit, the optimization algorithm and the parameter refinement strategy are discussed in detail.

Abstract: A method and system for indexing powder diffraction data are disclosed comprising choosing a maximum impurity peak tolerance level for a crystallography data search, choosing a range of number of calculated peaks for possible indexing solutions having a minimum number of peaks and a maximum number of peaks, selecting a crystal system to search, selecting powder extinction classes to search for indexing solutions, performing an exhaustive unit cell search of each of the selected powder extinction classes using a successive dichotomy approach to determine a set of indexing results, and ranking the obtained solutions according to likelihood.

Abstract: A method and system for indexing powder diffraction data are disclosed comprising choosing a maximum impurity peak tolerance level for a crystallography data search, choosing a range of number of calculated peaks for possible indexing solutions having a minimum number of peaks and a maximum number of peaks, selecting a crystal system to search, selecting powder extinction classes to search for indexing solutions, performing an exhaustive unit cell search of each of the selected powder extinction classes using a successive dichotomy approach to determine a set of indexing results, and ranking the obtained solutions according to likelihood.