The First Tetrahedrally Bonded Diamond–Like Compounds with Metallic Conductivity

In this paper we report for the first time the discovery of metallic conductivity in some tetrahedrally bonded diamond–like ternary oompounds 1 v vl with the general formula A3B C4 · Such compounds are characterized by a Valence Electron Concentration (VEC) of four valence electrons per atom. The preparation and characterization of one of the investigated compounds Cu3AsSe4 will be presented.The transition metal atoms in such a compound are connected by non-transition metal atoms (Se) via coordinate locallized bonds in a tetrahedral environment. Such an environment should lead to a splitting in the 3d filled orbitals of the transition metal because of lattice field. A delocalization of the 3d electrons is expected to take place via back donation, through an overlap with the empty antibonding orbitals on the non-metal atoms to minimize the negative formal charge on the transition metal atoms. If such an overlap leads to continuous electron path through the whole material, metallic conductivity could be visualized. The detailed bonding model will be discussed.