Method development

The development of methods which complete a structural model in an automatic way, in the case of 'difficult' compounds (these difficulties may arise from various causes like poor crystal quality, bad experimental data, superstructure effects, low resolution, unknown composition, pseudo-symmetry, etc.), has resulted in a new version of DIRDIF, a computer program system for crystal structure determination by Patterson methods and direct methods applied to difference structure factors. This new version of DIRDIF, a complete package for structure determination from single-crystal X-ray diffraction data, is also distributed on World Wide Web and has already found its way to many users all over the world (see also the Method Development section). Single-crystal X-ray diffraction is a very powerful method to study molecular interactions in the solid state. Moreover, crystal structures can form the basis for molecular modelling studies which improve the understanding of the intermolecular interactions involved.