Structural transformation yielding an unusual metallic state in liquidAs2S3under high pressure

Abstract

The ${\text{As}}_{2}{\text{S}}_{3}$ melt at room pressure represents a liquid having a three-dimensional network structure, semiconducting properties, and a huge viscosity. We have found that under high pressure a considerable change in the medium and short-range structure of this liquid is observed. Intermediate-range order correlations in the atomic arrangement almost disappear under pressure and an increase in the coordination number is observed. This increase is evidently associated with the formation of a significant fraction of the wrong neighbors As-As. At pressures above 6 GPa, the ${\text{As}}_{2}{\text{S}}_{3}$ melt has a conductivity close to the minimum conductivity value of $\ensuremath{\sim}100\text{ }{\text{Ohm}}^{\ensuremath{-}1}\text{ }{\text{cm}}^{\ensuremath{-}1}$ and a moderate viscosity of $\ensuremath{\sim}0.5--1\text{ }\text{Pa}\text{ }\text{s}$. Obviously, the transition under high pressures to such ``strange metallic'' liquids are bound to be seen in many other chalcogenide melts with network structure.