SYNTHESIS, CRYSTAL-STRUCTURE, AND ELECTRONIC-STRUCTURE OF INCDBR3

Colorless crystals of diamagnetic InCdBr3 are synthesized from element al Cd in an InBr3 melt. The new phase crystallizes in the orthorhombic NH4CdCl3 structure type (a = 944.7(2) pm, b = 410.47(8) pm, c = 1545. 5(3) pm, Pnma, and Z = 4). Cd2+ is octahedrally coordinated by Br- ani ons whereas the monovalent In+ cation is located in a strongly distort ed trigonal Br- prism, tricapped by other Br- anions. Semiempirical ba nd structure calculations (CSC-EH-TB) show moderately strong covalent contributions to In+-Br- bonding, similar to those found in the binary In/Br crystal chemical system. The quality of the semiempirical calcu lations is compared in detail with ab initio band structure computatio ns (TB-LMTO-ASA). Valence charge density plots based on the latter dis prove the existence of a directed electron ''lone-pair'' residing on m onovalent In+. (C) 1995 Academic Press, Inc.