X dependence of the electronic properties of cubic NaxWO3.

Abstract

Analysis of a variety of experimental data for cubic ${\mathrm{Na}}_{\mathrm{x}}$${\mathrm{WO}}_{3}$ (0.5\ensuremath{\le}x\ensuremath{\le}1) indicates that the electronic structure changes significantly with composition x. The lower--conduction-band width decreases and the band gap increases with increasing x. A simple theoretical model is developed which describes the x dependence of the electronic properties of cubic ${\mathrm{Na}}_{\mathrm{x}}$${\mathrm{WO}}_{3}$. The model provides closed-form analytical expressions for the energy bands, and the total and partial density-of-states functions. Results are obtained for the electronic specific heat, effective mass, magnetic susceptibility, and photoemission energy distribution curves of ${\mathrm{Na}}_{\mathrm{x}}$${\mathrm{WO}}_{3}$. These results are shown to agree with experimental data much better than the results of the rigid-band model.