The electronic structure of trigonal Se and Te for pressure near the phase transition points

Using a self-consistent pseudopotential approach, band structures and charge densities have been calculated for trigonal Se and Te at hydrostatic pressures just below the transition to the metallic phase. The results are compared to zero pressure calculations and experimental data. Very good agreement between experimental and theoretical results for the pressure dependence of the fundamental gap is found in both substances. Remarkable similarity is obtained between the Se and Te band structures at their respective phase transition points. This suggests that the transition leads to very closely related crystal structures.