Atomic structure and bonding properties in amorphous Cux(As2S3)1−x by ab initio molecular-dynamics simulations

It is known that the addition of few percent of Cu into chalcogenide glasses suppress the photodarkening. However, the precise nature of the mechanism that gives rise to this phenomenon still remains elusive. In order to gain some insights about the microscopic mechanism of this behavior, understanding of the fundamental materials properties is indispensable. In the present study, we investigated the composition dependence of the atomic structure and bonding properties in amorphous Cux(As2S3)1−x (x = 0, 0.11) by the ab initio molecular-dynamics simulations. We have found that the electronic density of state near the top of the valence band changes appreciably by the addition of Cu. In particular, a large change in the partial electronic density of states of the chalcogen component has been observed. The pair distribution function obtained indicates that the As–As correlation is influenced appreciably by the addition of Cu, whereas the changes in S–S and As–S correlations are relatively small. Our result also indicates that the Cu introduced tends to bind with S with a well defined bond length. The presence of Cu–As bonding and a possible agglomeration of Cu atoms have been also pointed out.