Structural aspects of the metal–insulator transition in BaVS3

A sequence of structural transitions occurring in the quasi-one-dimensional (1D) 3d system BaVS3 at low temperature was investigated by high resolution synchrotron X-ray diffraction. The orthorhombic Cmc21 structure of the intermediate-temperature (70Ksuperstructure (with Im symmetry) is proposed and refined. The formation of the superstructure is associated with the stabilization of a mixed bond order / charge density wave.