Structural and electronic properties of α-Sn, CdTe, and their [001] monolayer superlattices

A systematic study of the structural and electronic properties of α-Sn, CdTe, and their [001] monolayer superlattices (namely, ${\mathrm{SnTe}}_2$Cd, ${\mathrm{SnCd}}_2$Te, and ${\mathrm{Sn}}_2$CdTe) using the total-energy local-density all-electron full-potential linearized augmented-plane-wave method is presented. Our results show that (i) good agreement with experiment is obtained for the ground-state properties of the pure constituents; (ii) ‘‘compensated’’ ${\mathrm{Sn}}_2$CdTe is unstable with respect to phase separation; (iii) the substitution of Sn for Te is energetically the most unfavorable; (iv) large tetragonal distortions are found when Sn is substituted for Cd, while bond-length conservation is found when Sn replaces Te; (v) all the structures studied show (within the local-density approximation) a direct band gap higher than that of pure α-Sn; (vi) in all the structures considered, the direct gap is favored over the indirect Γ-L gap.