Synthese et structure cristalline de Ba 1.14K 0.72VS 4

Abstract

Single crystals of a new compound, Ba 1.14K 0.72VS 4 have been obtained from a flux of KCl at 950°C. This is the first quaternary sulfide in the BaKVS system and it is a diamagnetic insulator at room temperature. The compound has orthorhombic symmetry, Pna2 1, with unit cell dimensions a = 9.158(2)Å, b = 12.144(3)Å, c = 6.729(1)Å, Z = 4. Its structure was determined using heavy-atom methods and refined to an R value of 0.031 ( wR = 0.022); 5654 intensities were measured, using Ag Kα radiation. The structure is related to K 2SO 4-β but is not centrosymmetric and the surroundings of the potassium atoms are different. Barium and potassium atoms are coordinated, respectively, to 9 and 11 sulfur atoms, forming polyhedrons which can be described as capped trigonal prisms. The vanadium cations, V 5+, are tetrahedrally coordinated to sulfur atoms. The 0.72 potassium and 0.14 barium atoms share the same crystallographic site, explaining the relative high value of the thermal parameters.