Behaviour of the optical gap of trigonal Se under pressure

The behaviour of the optical gap of trigonal Se under pressure is studied up to 140 kbar using the self-consistent symmetrized OPW method. We conclude that (i) the minimum optical gap at zero pressure is indirect M₂ → H₁, (ii) the change of the minimum optical gap from M₂ → H₁ to H₃ → H₁ causes the anomaly found in the experimental absorption edge at 35–50 kbar, and (iii) the gap is not expected to close at 140 kbar.