High pressure phases and the structural phase transition of selenium

We studied the structural phase transition of Se under high pressure by means of a full-potential linearized-augmented-plane-wave met hod. We calculated the electronic structure and the total energy at various volumes for the beta-Po type rhombohedral and the hcc structure, from which we estimated the transition pressure. It was found that a first-order phase transition appears at a much lower pressure than the observed value with a small volume reduction. The structural properties calculated were discussed and compared with the available experimental data.