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.