We have investigated the ionic relaxations, electronic structures, and optical properties for ${\mathrm{Cd}}_{1-x}{\mathrm{Zn}}_x\mathrm{Te}$ alloys using density functional theory. The quasi-zinc-blende structure is used with special emphasis on the relaxation behaviors of ${\mathrm{Te}}^{2-}$ around either ${\mathrm{Cd}}^{2+}$ or ${\mathrm{Zn}}^{2+}$. Our calculations confirm that the relaxations of the anion rather than the cation contribute primarily to the alloying process as predicated by the experiments. The differences in the ionicity of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Zn}}^{2+}$ and their configurations around ${\mathrm{Te}}^{2-}$ are responsible for the different relaxation behaviors of ${\mathrm{Te}}^{2-}$. A striking result is the relevance of the relaxation behaviors of ${\mathrm{Te}}^{2-}$ with the alloying effect on the electronic states. This result supports the electronic features of ${\mathrm{Cd}}_{0.5}{\mathrm{Zn}}_{0.5}\mathrm{Te}$ alloy reported by the systematic analyses with quasirandom structure. The band structures obtained here are used to determine the optical functions. The comparison with the available experimental and theoretical results suggests an overall topological resemblance in the present dielectric function spectra when the band-gap correction is included.

• Received 21 June 2006

DOI:https://doi.org/10.1103/PhysRevB.76.035209