Application of the Embedded Cluster Method to the Electronic State of Silicate Glasses

Abstract: The discrete variational (DV) X_α method is used to investigate the electronic structure of silicate glasses in the embedded cluster model. Effects of the cluster size and the size of embedding units on electronic states are discussed. The embedding unit greatly improves the electronic state description compared with an isolated SiO₄^4- cluster, which is a structural unit of silicate glasses; e.g., the Fermi energy becomes -7.20 eV in the embedded cluster, while that of the isolated charged cluster is +23.8 eV. More importantly, both Si and O ions become more ionic in the embedded clusters. The size of both embedding units and variational cluster, however, is not very critical to electronic states localized around the center of the clusters.