Structural study of GeS2 glasses permanently densified under high pressures up to 9 GPa

The structures of GeS2 glasses permanently densified under 1.5, 3.0, 4.5, 6.0 and 9.0 GPa have been investigated by means of Ge–K EXAFS, Ge–K and S–K XANES, X-ray radial distribution, Raman scattering and optical absorption. The experimental results have been analyzed based on the structures of α (high-temperature form)-, β (low-temperature form)- and II (high-pressure form)-GeS2 crystals. The densities of permanently densified glasses increased monotonously with increasing applied-pressure until 6.0 GPa and then reached a constant value in a pressure range from 6.0 to 9.0 GPa. With increasing densification the structure of GeS2 glass, which is an intermediate between the structures of α-GeS2 and β-GeS2 at atmospheric pressure, was progressively converted into a II-GeS2-like structure with no large hollows. The red shift of optical absorption edge in the visible region that results from densification exhibited the same pressure dependence as that observed for density.