High Pressure Crystalline Structures of Se at Low Temperature

The low-temperature high-pressure structures of elemental selenium (Se) have been characterized by insitu x-ray diffraction in a diamond anvil cell. A phase diagram appropriate for the P-T conditions is constructed from the results. Unlike the closely related elemental barium (Ba), no new structure was found by first cooling the sample to 10 K and then compressed to 34 GPa. The results confirmed the structure of the superconducting phase observed at 13 GPa,