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 Hamiltonian for selenium, based on the fitting of cohesive energy curves obtained from density-functional calculations for solid phases, rings, and chains structures. We have assessed the model by means of various tight-binding molecular-dynamics calculations performed in liquid and amorphous states. Comparisons with ab initio calculations and experimental results indicate that the model is fairly accurate for the pair structure at low and medium temperatures, 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 states predicts the occurrence of a semiconductor-to-metal transition when approaching the critical temperature in good agreement with ab initio calculations and experimental evidence.