Electronic structure calculations for the ternary intermetallic compounds A(2)MX and AMX(2) (A=Li; M=Rh, Pd, Ir, Pt; X=Al, Ga, In) using density-functional theory

The electronic structure of the ternary intermetallic compounds A(2)MX and AMX(2) (A Li; M=Rh, Pd, Ir, Pt; X=Al, Ga, In) was investigated by density-f unctional theory within the local density approximation. The band structure s and the chemical binding were analyzed in terms of orthogonal orbital pro jections. The results confirm the existence of a covalently bound MX sublat tice as assumed in the Extended Zintl Concept. The analysis indicates stron g hybridization between metal d and ligand p orbitals with some participati on of metal s and ligand s and a direct X-X interaction in LiMX2. The metal ligand interaction increases in the order Pd<Pt<Rh<Ir independently of X. With respect to X the covalent character decreases from In and Ga towards A l. The location of the metal d band differs considerably between the group 9 elements Rh and Lr and the group 10 elements Pd and Pt. All investigated compounds are predicted to be metals, in spite of the ionic description use d in the Extended Zintl Concept. The metallic behavior is in agreement with experimental results from photoemission studies. This is also the case for the predicted character of the valence band and its dependence on the meta l atom. (C) 2001 Elsevier Science B.V. All rights reserved.