A first principle investigation of the non-synthesized cubic perovskite LiGeX3 (X=I, Br, and Cl)

Abstract

A self-consistent calculation within Density Functional Theory (DFT) using norm-conserving pseudopotential plane-wave and the precise hybrid functional HSE06 were performed. The stability, elastic, originatemechanical, electronic, and optical properties of the cubic perovskites LiGeX3 (X = Br Cl, and I) are investigated. The behaviour of the stability and elastic characteristics under hydrostatic pressure is also presented and studied. Band structure analysis using PBE, GW-Approximation, and HSE06, show that LiGeX3 (X = Br Cl, and I) are direct bandgap semiconductors. The structures are most stable at the computed relaxed lattice parameters (a=b=c=5.880,5.470and5.190Ao)for the LiGeI3, LiGeBr3, and LiGeCl3, respectively. The Pressure dependence of cubic perovskite elastic moduli, bulk modulus B, shear modulus/constant (G,Cs), Young's modulus E, the Poisson's ratio σ, Vickers hardness Hv, Lame's constants (λ,μ), Cauchy pressure C12−C44, the Anisotropy factor A, Kleinman parameter ζ, and the P-wave modulus Pw, elastic wave velocities v, Debye temperature θD is presented. The optical properties including the static refractive index and dielectric constant are found to be related to the direct bandgaps, proportionally. The refractive index, extinction coefficient, complex dielectric function, energy loss function, optical conductivity, reflectivity, and absorption coefficient for 0–25eVincident photon energies are also presented.