COMPUTATIONALLY ASSISTED STRUCTURE DETERMINATION FOR MOLECULAR MATERIALS FROM X-RAY-POWDER DIFFRACTION DATA

For organic molecular materials, the key step in solving crystal struc tures from high-resolution powder diffraction data is the generation o f reliable trial structures for final refinement. In this paper we dem onstrate an efficient new methodology for generating trial structures that predicts the correct molecular packing in a crystal lattice given the unit cell dimensions and space group. The method uses a systemati c search of intermolecular, atom-atom interactions to examine and rank all possible packing arrangements. The approach is demonstrated for a number of systems with increasing degrees of search complexity includ ing indigo, 6,13-dichlorotriphendioxazine, phenanthrene, paracetamol, and benzophenone. The final example is of particular importance as it illustrates the first application of this type of methodology to a con formationally flexible system.