First-Principles Calculations of the Structural, Electronic, Elastic and Optical Properties of LiGaS2 and LiGaSe2 Semiconductors Under Different Pressures

The structural, electronic, elastic and optical properties of LiGaS2 and LiGaSe2 orthorhombic crystals have been studied using local density approximation and general gradient approximation within first-principles density functional theory calculations. The lattice constants, energy band gap, total density of states and partial density of states have been calculated. The pressure-dependence of elastic stiffness constants (Cij), bulk modulus (B), shear modulus (G), Poisson’s ratio (υ), Young’s modulus (γ) and B/G ratio have been calculated at 0 GPa, 10 GPa, 20 GPa, and 30 GPa pressures. The optical properties such as dielectric constants, absorption spectra, refractive index, extinction coefficient, reflectivity and energy-loss spectra have also been estimated under 0 GPa, 10 GPa, and 20 GPa pressures in the energy range 0–15 eV. The values of 14 elastic and 3 optical parameters have been calculated at different pressures. The estimated values agree well with the known values.