CRYSTAL STRUCTURE DETERMINATION FOR PHARMACEUTICAL MATERIALS FROM POWDER X-RAY DIFFRACTION COMBINED WITH MOLECULAR MODELLING

摘要

A preliminary validation study has been carried out to test a new simulated annealing algorithm for the generation of trial crystal structures, for molecular materials, in fixed unit cells determined from powder diffraction data. The search space is defined by three rigid body translations, three rigid body rotations and the number of internal rotations required to describe the molecular conformation. The method employs a calculated lattice energy, modified to take account of changes in molecular conformation, as the objective function for the search space. Two polymorphs of the pharmaceutical material primidone, with previously determined crystal structures were used to test the method. The results are compared with those generated by an existing systematic search algorithm.