First-principles calculations of optical properties of Zn2GeO4 under high pressures

The structural, band-gap and optical properties of Zn2GeO4 under high pressures had been investigated using the first-principles calculations. The computed results at ambient pressure were in excellent agreement with available theoretical and experimental data. The results by LDA showed that the band gaps of Zn2GeO4 firstly increased and peak at around 9.7Gpa, and then gradually decreased with pressure increasing. The change in band-gap was due to the fact that covalent enhancement between atoms distance decrease and the delocalization action exceeded the force of bonding state. Furthermore, the dielectric function, absorption spectrum, and refractive index were obtained and analyzed on the basis of the DOS and the change in band gap for radiation up to 30 eV.