MS-WINDOWS SOFTWARE FOR SPACE GROUPS: APPLICATION TO DOMAIN STRUCTURE SYMMETRY ANALYSIS B.L. Davies, School of Mathematics, University of Wales, Bangor, Gwynedd, LL57 1UT, U.K., R. Dirl, Institut fur Theoretische Physik, TU Wien,A-1040 Wien, Wiedner Hauptstrasse 8 - 10, Austria, V. Janovec, Technical University of Liberec, Halkova 6, 461 17 Liberec 1, Czech Republic, Z. Zikmund, Institute of Physics, Academy of Sciences, Na Slovance 2, 180 40 Prague 8, Czech Republic

An integrated package of programs has been developed for IBM-Compatible PCs to investigate the structures and representations of crystallographic space groups. The package is implemented as a Microsoft Windows application using Borland Delphi with user code in Object-Pascal. Parts of this software have been adapted to assist in the symmetry analysis of domain structures. For a given phase transition the software identifies all domain states and finds, e.g. (i) symmetry groups of all domain states, (ii) all operations that transform a given domain state into another domain state, (iii) twinning groups and symmetries of ordered and unordered domain pairs,(iv) classes of crystallographically equivalent domain pairs with similar domain distinction. As an example of the use of the software we consider the symmetry analysis of domain structures in the 2H polytype TaSe₂ in which the disordered phase has P6(3)/mmc (#194) symmetry and the ordered commensurate phase exhibits Cmcm (#63) symmetry.