In situ EXAFS study on GeS2 glass under high-pressure

A GeS2 glass was compressed up to 8 GPa at room temperature, heated up to 270 °C under 8 GPa and then decompressed to ambient pressure at room temperature, using a large volume high-pressure apparatus. The local structural-changes around Ge were examined by means of an in situ EXAFS method. The Ge–S bond length became monotonously short with increasing applied-pressure up to 8 GPa at room temperature. When the specimen was heated to 270 °C under 8 GPa, however, the bond length became slightly long. The elongated bond length was almost kept even after the temperature was descended to room temperature. In decompression process, the bond length became gradually long with releasing applied-pressure down to 2 GPa, following a change in compression process. Below 2 GPa, however, the Ge–S bond length was largely elongated, being longer than the initial one. No significant change of coordination number was found in the compression and decompression processes up to 8 GPa. This change can be explained by a combined effect of elastic and inelastic structural-changes.