ELECTRONIC-STRUCTURE, BONDING, AND PROPERTIES OF CUP2

A theoretical study of the electronic structure of CuP2 is presented on the basis of molecular orbital and tight-binding band calculations based upon the extended Huckel method. We examined the electronic factors leading to ethane- and diborane-like coordination arrangements of dinuclear compounds and found the diborane-like coordination geometry of the d10 ions in CuP2 to be favorable on electronic grounds. The analysis of DOS and COOP curves shows that there are two important contributions to Cu-Cu bonding: delocalized bonding involving the bridging phosphorus atoms in the Cu2P2 rings and through-space Cu(I)-Cu(I) interactions due to mixing of the occupied d(z)2 and empty s and p(z) orbitals. The electronic band structure of CuP2 has a substantial energy gap between the valence and conduction bands. The valence band is dispersive along the interlayer direction due to the coupling of the metal d orbitals through the polyphosphide sublattice.