Electronic and Optical Properties of Mg2GeO4 under Pressure Effect: Ab Initio Study

Abstract We report first-principles studies of the structural, elastic, electronic, and optical properties of Mg2GeO4 in orthorhombic structure, including pressure dependence of structural parameters, band structures, density of states, and optical constants up to 20 GPa. The calculated structural parameters are in good agreement with the available experimental values at zero pressure. The mechanical stability of Mg2GeO4 has been confirmed by calculation of the elastic constants and the non-uniform pressure dependence of the lattice parameters may also mean that Mg2GeO4 undergoes anisotropic compression. Meanwhile, the pressure dependence of the electronic band structure, density of states and partial density of states of Mg2GeO4 up to 20 GPa were presented. The band structures show a direct band gap for this compound and the calculated band gaps expend with increasing pressure. Moreover, the evolution of the dielectric function, absorption coefficient (α(ω)), reflectivity (R(ω)), and the real part of the refractive index (n(ω)) at high pressure are also presented. According to our work, we found that the optical absorption spectra of Mg2GeO4 undergo a blue shift with increasing pressure.