Synchrotron radiation diffraction of amorphous selenium under high pressure

High-pressure in situ energy dispersive X-ray diffraction (EDXRD) experiments on amorphous selenium(a-Se) have been carried out using a synchrotron X-ray source and a diamond anvil cell (DAC) up to 74.3 GPa at room temperature. The pressure-induced crystallization of a-Se has been found at the pressures between 10 GPa and 11 GPa, and the crystal structure is confirmed to be the mixture of hexagonal phase and a new high pressure metallic phase. It is noticeable that the new phase is still stable up to 42 GPa, and completely transformed to the orthorhombic phase after 42 GPa. Two structure phase transitions at about 60 GPa and 60 GPa have also been observed, which agree very well with Mao et al and Akahama et al, respectively, whose work were starting from the material of hexagonal selenium.