Crystallography in Four and Five Dimensions as Applied to Multi-Sublattice (Composite) Structures

摘要

Composite structures, containing two or more sublattices in one crystal, are of importance in the search for new materials. They are classified in terms of the interlattice matrix relating the sublattices, and by the use of chemical criteria. The use of superspace to interpret the diffraction pattern and perform calculations on electronic structure and lattice energy is referred to. The composite low-dimensional conductors (BEDT-TTF)Hg_(0.776)(SCN)2 and (BEDT-TTF)4Hg_(2.88)Br_8 (BEDT-TTF = bisethylene dithiotetrathiafulvalene) are discussed as examples. Of particular interest are the interaction between the sublattices and the change of structure and properties as a function of temperature.