Order, miscibility, and electronic structure ofAg(Bi,Sb)Te2alloys and (Ag,Bi,Sb)Te precipitates in rocksalt matrix: A first-principles study

Abstract

Using first-principles density-functional theory calculations and cluster expansion, we predict that ${\text{AgBiTe}}_{2}{\text{-AgSbTe}}_{2}$ alloys exhibit D4 cation order at all temperatures below melting and are fully miscible down to the room temperature and below. We also discuss the miscibility and ordering on the cation sublattice in quasiternary (Ag,Bi,Sb)Te alloys with general composition, within the subclass of structures with rocksalt topology (relevant for the case of coherent precipitates in a rocksalt matrix, e.g., in PbTe). The band structures of the ${\text{AgBiTe}}_{2}$ and ${\text{AgSbTe}}_{2}$ compounds and the evolution of the Fermi-surface topology at low hole dopings are presented. We use these results to refine the interpretation of the recent experimental measurements on naturally doped ${\text{AgSbTe}}_{2}$ samples reported by Jovovic and Heremans [Phys. Rev. B 77, 245204 (2008)] and present a simplified model of the band dispersion near the valence-band maximum.