Ab initio Calculations of Electronic Band Structure, Optical and Elastic Parameters of Solid-state CdTe-CdSe Solutions

Electronic band structure and elastic and optical properties are studied for the solid-state $\mathbf{CdTe}_{1-x}\mathbf{Se}_{x}(x=1/16$ and 15/16) solutions, using a density functional theory and a CASTEP code. The structures of the samples are deduced issuing from the ‘parent’ compounds $\mathbf{Cd}_{16}\mathbf{Te}_{15}$ and $\mathbf{Cd}_{16}\mathbf{Se}_{16}$. A cubic structure of the ‘parent’ compounds is taken. The bandgap of $\mathbf{CdTe}_{1-x}\mathbf{Se}_{x}$ is found to be of a direct type for all of the solid-state solutions under test. Basing on the electronic band structure, we obtain the effective electron mass, the effective masses of holes corresponding to different energy levels, and the reduced carrier mass at the $\mathbf{G}$ point of Brillouin zone. The optical parameters such as exciton-binding energy, refractive index and high-frequency dielectric constant are calculated, too. The elastic properties such as the Young, shear and bulk modules are predicted, along with and the Poisson ratio. Using the data for the elastic coefficients, the acoustic velocities and the Debye temperature are obtained. All of the calculated parameters correlate well with the known experimental data.