Calculations and Analysis of the Electronic Structures of Transition-Metal Phosphosilicides Cu4SiP8, IrSi3P3, CoSi3P3, and FeSi4P4

Abstract Electronic structures of phosphosilicides Cu 4 SiP 8 , IrSi 3 P 3 , CoSi 3 P 3 , and FeSi 4 P 4 were calculated using the extended Huckel tight-binding method and were analyzed in terms of a modified electron counting scheme. The d -block levels of these compounds appear well below the Fermi level, thereby indicating that the transition-metal atoms exist as d 10 ions. Except for the case of IrSi 3 P 3 , the d -block energy levels of these compounds occur in a narrow energy window less than 1.5 eV wide. The Si 3 p orbitals act as acceptor orbitals to the transition-metal d orbitals in IrSi 3 P 3 , CoSi 3 P 3 , and FeSi 4 P 4 .