Abstract

A first-principles study of the insulator-to-metal transition under pressure in NbS3 is reported. In contrast with previous proposals, it is found that the transition is not due to a progressive closing of the initial band gap but to the inversion of the relative stability of two different polymorphs under pressure. The Fermi surface of the new metallic state under low pressure (polymorph V') is discussed, and the possible occurrence of as yet unknown incommensurate phases is suggested. The reason for the inversion of stability of the two polymorphs is discussed.