ChemInform Abstract: Structure-Bonding Relationships in the Laves Phases.

Abstract

The Laves phase structures (MgCu2 MgZn2 and MgNi2 types) are adopted by a large number of binary intermetallic compounds of composition AB2. These phases belong to the class of tetrahedrally closepacked alloys. Two of the structural features of the Laves phases which have aroused interest are, firstly the dependence of the structure adopted (especially the choice between the cubic MgCu2 and hexagonal MgZn2 types) on the number of valence electrons of the constituent metal atoms and, secondly the structural distortions observed in a number of the hexagonal MgZn2 type phases. By performing extended Huckel band calculations on model AB2 compounds with both the cubic and hexagonal structures and on the B sub-nets alone, structure electron-count and deformation-electron count correlations are derived. These correlations depend on the highly peaked nature of the density of states of the Laves phases, primarily due to the B network.