Topological analysis of ionic packings in crystal structures of inorganic sulfides: the method of coordination sequences

Using the concept of coordination sequences and the uniformity criterion the method of topological analysis of atomic packings and of their classification at any degree of metric distortions is implemented in the computer program IsoTest. The criterion is based on the search for packings topologically similar, but not equal to close packings. The topological analysis of ionic sublattices was employed for the crystal structures of 781 inorganic sulfides. It was shown that no less than in the third of cases the sulfides are constructed on the basis of a distorted close packing, and such packings are constructed with sufficiently large cations, as a rule. The examples of forming close packings by complex thioanions contained in a number of thiosalts were drawn.