Relation between Electronic Structure andTcin Binary and Ternary Molybdenum Chalcogenides

Abstract

Localized orbital calculations are presented for the electronic structure of Chevrelphase molybdenum chalcogenides. Densities of states at the Fermi energy, $N\left(E_{\mathrm{F}}\right)$, are found to depend sensitively on the modification of intercluster interactions because of lattice distortions introduced by the ternary component. Calculated $N\left(E_{\mathrm{F}}\right)$ values in ${\mathrm{Mo}}_6$ ${\mathrm{S}}_8$, Pb${\mathrm{Mo}}_6$ ${\mathrm{S}}_8$, ${\mathrm{Mo}}_6$ ${\mathrm{Se}}_8$, and Pb${\mathrm{Mo}}_6$ ${\mathrm{Se}}_8$ are 0.5, 1.7, 1.1, and 0.9 states/(spin Mo-atom eV), respectively, and show a strong correlation with $T_c$. States near to $E_{\mathrm{F}}$ are strongly confined within ${\mathrm{Mo}}_6$ octahedra.