Structural, elastic, electronic and optical properties of the quaternary nitridogallate LiCaGaN2: First-principles study

Abstract

First-principles density functional theory calculations were performed to predict some of the not yet explored physical properties of the monoclinic quaternary nitridogallate LiCaGaN2. The calculated lattice parameters, including the lattice constants, angle β and internal atomic coordinates, are in excellent agreement with the corresponding measured ones, proving the reliability of the chosen theoretical approach. The equation of state, pressure dependence of the lattice constants, unit cell volume, angle β and bond-lengths were explored in detail. The single-crystal and polycrystalline elastic constants and their pressure dependence were numerically estimated. The mechanical stability, ductility/brittleness, average elastic wave velocity, Debye temperature and elastic anisotropy were also assessed. The electronic structure and its evolution with external applied hydrostatic pressure were explored. The bonding character was demonstrated by calculating the site-projected density of states, charge density and effective Mulliken charges of all ions. The effective masses of the charge-carriers were numerically estimated. The complex dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity and electron energy-loss function spectra were calculated for different polarizations of the incident light. Pressure dependence of the static dielectric constant, static refractive index and static reflectivity are also reported. To the best of our knowledge, this is the first attempt to explore the aforementioned physical properties for the title material.