Quantum-Chemical Modeling of the Effect of a Continuous Random Network on Stabilization of Charged and Neutral Defects in a-S

Abstract

Quantum-chemical modeling of the stabilization of neutral and charged defects in amorphous sulfur (a-S) has been carried out. The atoms constituting the three nearest coordination spheres of a defect were modeled using the cluster approximation at the HF/6-31G* level. The interaction of the defect region with distant fragments of a continuous random network was calculated using the polarizable continuum model (PCM), in which the medium surrounding the cluster was considered as a continuum with the experimental permittivity for a-S. The energy of formation of charged defects Edef based on threefold coordinated sulfur atoms (C3+, 3−)is close to the homolytic bond cleavage energy Eb. For neutral defects, Edef < Eb. Such defects can be the sites with a negative correlation energy, which are responsible for specific properties of chalcogenide glassy semiconductors.