Abstract
Electrical resistance measurements, x-ray diffraction and Raman scattering experiments have been carried out under high pressure for Se allotropies. α-monoclinic Se showed a transition to the metallic state at 12 GPa, which was considerably lower than 23 GPa of trigonal Se. Corresponding to the metallization, a structural transition to a new high-pressure phase, which could not be explained by any metallic phase of Se reported previously, was observed in α-monoclinic Se. Raman data supported this result. In amorphous Se, crystallization was observed at 12 GPa. The diffraction pattern after crystallization was explained as the coexistence of the new high-pressure phase and trigonal Se. These results have established the double nature of the sequence of the structure in the pressure-induced phase transition of Se.
