Band structure calculations of high pressure phases of selenium

We report a detailed theoretical calculation of the electronic band structure of Se in hexagonal and monoclinic phases under pressure. The first principle tight-binding linear Muffin-Tin orbital method (TBLMTO) within local density approximation (LDA) has been used. The total energy calculations have been carried out within the atomic-sphere approximation (ASA) for both phases in order to study the phase stability. Apart from the electronic band structure and structural stability calculations, the density of states (DOS) and Fermi energies at various pressures are calculated. The calculated lattice parameters, transition pressure, bulk modulus and the pressure-volume relation were found to be in good agreement with recent experimental results. Our calculations show that the ambient pressure hexagonal phase has a band gap of 1.49 eV whereas the high pressure monoclinic phase is found to be metallic. (author)