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

Electronic structures of phosphosilicides Cu4SiP8, IrSi3P3, CoSi3P3, and FeSi4P4 were calculated using the extended Hückel 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 d10 ions. Except for the case of IrSi3P3, the d-block energy levels of these compounds occur in a narrow energy window less than 1.5 eV wide. The Si 3p orbitals act as acceptor orbitals to the transition-metal d orbitals in IrSi3P3, CoSi3P3, and FeSi4P4.