Quantum chemical simulation of hypervalent defects in non-crystalline sulfur

Abstract

Different kinds of formation of multicenter hypervalent defects were investigated on MNDO level with the use of systems simulating infinite sulfur chains. It was found that threecenter defects may be easily formed through the interaction of charged fragments (both positively and negatively) with one or two infinite chains. However, concentration of such defects is probably low as the formation of charged splinters needs a high energy expenditure. For neutral systems different variants of drawing together of both two or three chains and a chain with a small S kfragment (k=2−5) do not lead to formation of an additional chemical bonding. In these calculations three metastable neutral hypervalent defects were found. The first one is formed by coordinating 4 half-infinite chains to the central S atom, the second one is generated through the interaction of a singlet S atom with one or two chains. In the last case threecenter defects form “bridges” between molecular fragments. The third defect arises through the transformation of the second one into a cyclic structure. There exists a possibility of bond switching.