Evidence for valence alternation, and a new structural model of amorphous selenium

A molecular-dynamics simulation has been carried out for amorphous selenium. The simulation used 64 atoms in a constant volume simple cubic cell. The pair correlation function, g…r†, and structure factor, S…Q†, were computed and compared with experimental and previous theoretical studies. The average coordination number is exactly 2. Only one defect, an intimate valence alternation pair type defect was produced. The electronic density of states and the localization of the electronic state also manifest some properties of valence alternation pair defect type. The results give new evidence for valence alternation in a-Se. Ó 1998 Published by Elsevier Science B.V. All rights reserved. PACS: 61.43.Dq; 71.23.-k; 71.23.Cq