Electronic structure of metallic liquid Se-Te alloys

Experimental data for the electrical conductivity σ, the thermopower S, and the magnetic susceptibility χ are analyzed for alloys ${\mathrm{Se}}_{\mathrm{x}}$ ${\mathrm{Te}}_{100\mathrm{-}\mathrm{x}}$ in the metallic and near-metallic range of compositions x=0 to 50. Comparison of the behavior of σ and S in the region where the metallic approximation to the transport coefficients is valid shows that σ($E_F$) is proportional to the Fermi energy $E_F$ for x=10 and 20. In view of the validity of the diffusive model for transport, this corresponds to a parabolic density of states N($E_F$). At x=30, it is found that N($E_F$) changes to a linear dependence on $E_F$, in keeping with the beginning of band tailing as the Fermi energy approaches the edge of the valence band. For x≤30, the experimental behavior of the paramagnetic susceptibility ${\chi }_P$ confirms independently the shape of N($E_F$) deduced from σ and S, and comparison of the three experimental variables yields numerical values for the band parameters. At x=40 and 50, where analysis requires the use of Fermi-Dirac integrals, the behavior of σ and S is still consistent with a linear N(E), but the behavior of the experimental ${\chi }_P$ indicates that the spin states are separating from the valence band as the temperature is decreased.