Crystal structure and physical properties of Cu075VS2

A new compound with composition Cu0.75VS2 has been prepared. Its preparation, X-Ray structure, electrical and magnetic properties are reported. The structure is related to the CdI2-type, as in the case of the previously described Cu/sub x/TiS2; in Cu0.75VS2, Cu atoms are ordered in tetrahedral sites between the CdI2-type subunits, whereas in Cu/sub x/TiS2 Cu atoms are disordered in two independent sites. The vanadium atoms are shifted with respect to the titanium sites which leads a monoclinic distortion of the hexagonal cell. The relation between the CdI2 unit cell and the true monoclinic cell of Cu0.75VS2 is found. In Cu0.75VS2, vanadium atoms occupy two independent sites, three vanadium atoms forming a triangular cluster (V2-V3 distances are 2.91 A and V3-V3 are 2.92 A) while one vanadium atom is isolated (V1-V2 = 3.36 A and V1-V3 = 3.37 A). The physical properties exhibit a transition at 500K approximately, the magnetic susceptibility being temperature-independent above and temperature dependent below the transition (Curie-Weiss behavior). Resistivity and Hall measurements confirm the metallic nature of the compound and show the existence of the low temperature transition. The observed properties could be interpreted as a result of the low-temperature localization of the 3d electron of V1