Ab initio study of physical properties of some solid materials

Abstract

The structural, electronic, optical, elastic and thermoelectric properties of the ternary Zintl compounds Sr3GaAs3, Ba3GaAs3 and Ba2ZnP2 were studied using two complementary first-principles calculation methods, the pseudopotentials plane waves (PP-PW) and the full potential Linearized Augmented Plane wave (FP-LAPW) methods within the density function theory framework. Sr3GaAs3 and Ba3GaAs3 crystallize in an orthorhombic system, space group Pnma (no 62), while Ba2ZnP2 crystallizes in an orthorhombic system, space group Ibam (no 72). GGA-PBEsol was used to treat the exchange and correlation potential (XC) to calculate the structural and elastic properties. GGA-PBEsol and TB-mBJ were used to study its electronic and optical properties. The values of structural parameters (the parameters and volume of primitive cell) calculated agreed well with available experimental data. This indicates the reliability of our results. We have numerically estimated the elastic constants and associated properties (elastic constants Cij, Young's modulus E, shear modulus G, Poisson's modulus  and Debye temperature D) for single-crystal and polycrystalline under zero pressure and anisotropic sound velocities. The calculation results showed that the studied compounds belong to the semiconductor family, with direct band gaps for the compounds Sr3GaAs3 and Ba3GaAs3, valued at 1.271 eV and 1.285 eV, respectively, and an indirect band gap energy with a value of 1.24 eV for Ba2ZnP2. We analysed the electronic states of the energy bands using partial density diagrams of states. Optical constants were calculated in an energy range from 0 to 30 MeV. The results of the calculations showed an increase in the static dielectric constant () with a decrease in the energy impedances of the studied compounds. The thermoelectric constants of the compounds were studied using semiclassical Boltzmann transport theory. Our results indicate that Ba2ZnP2 has a best figure of merit (ZT) of 1.77 at 300 K, making it a potential candidate for thermoelectric applications.