Tight-binding model of selenium disordered phases

Following the parametrization scheme first introduced by Goodwin, Skinner, and Pettifor, we propose here a model of the empirical tight-binding Hamilt onian for selenium, based on the fitting of cohesive energy curves obtained from density-functional calculations for solid phases, rings, and chains s tructures. We have assessed the model by means of various tight-binding mol ecular-dynamics calculations performed in liquid and amorphous states. Comp arisons with ab initio calculations and experimental results indicate that the model is fairly accurate for the pair structure at low and medium tempe ratures, but tend to overestimate bonding at high temperatures. The number of valence alternation pair defects also seems to be overestimated. On the other hand, the band structure derived from the tight-binding density of st ates predicts the occurrence of a semiconductor-to-metal transition when ap proaching the critical temperature in good agreement with ab initio calcula tions and experimental evidence. [S0163-1829(99)02333-4].