Structural phase transitions and equations of state for selenium under pressures to 129 GPa

By the use of energy-dispersive x-ray diffraction with synchrotron radiation, pressure-induced structural phase transitions and equations of state were studied on Se in the extended pressure range up to 129 GPa. In contrast to a previous study on Se to 50 GPa, the higher resolution with synchrotron radiation in the present study allowed for an unambiguous identification of the structure for Se-IV as rhombohedral ({β}-Po type) with one atom in the rhombohedral unit cell, and thus, a close similarity to Te under pressure and Po at higher temperatures is reestablished.