Elastic, electronic and optical properties of the filled tetrahedral semiconductor α-LiCdAs

We have investigated the elastic, electronic and optical properties of the Nowotny–Juza filled tetrahedral semiconductor α-LiCdAs using the pseudo-potential plane-wave within the density functional theory. A numerical first-principles calculation of the elastic constants was used to calculate C11, C12 and C44. The values of the sound velocities in different directions have been calculated. The isotropic elastic moduli, namely bulk modulus, shear modulus, Young's modulus, Poisson's ratio and Lamé's constants are calculated in framework of the Voigt–Reuss–Hill approximation for ideal polycrystalline α-LiCdAs aggregate. We estimated the Debye temperature of α-LiCdAs from the average sound velocity. The analysis of the site and momentum projected densities and charge density reveals strongly covalent Cd–As and strongly ionic Li–As bonds. Band structures show that α-LiCdAs is a narrow direct band gap. The variation of the fundamental band gap versus pressure is well fitted to a quadratic function and a direct to an indirect band gap transition occurs at 15.30 GPa. Furthermore, the dielectric function, optical reflectivity, refractive index, extinction coefficient and electron energy loss are calculated for radiation up to 20 eV. The results are compared with the available experimental and theoretical results.