Synthesis, crystal structures, magnetic properties, and lattice dynamics of Ba2XCu(OH)[V2O7] with X=Cl, Br

We have synthesized Ba2XCu(OH)[V2O7] with X=Cl, Br by hydrothermal methods. The isotypic structures (Pnma, Z=4, a approximate to 15.1 angstrom, b approximate to 6.1 angstrom, c approximate to 9.6 angstrom) contain distorted hexagonal layers of Ba and X in a BN-type arrangement. Each halide is further coordinated by one out-of plane Ba atom in an alternate up-down fashion resulting in an overall (2)(infinity)[Ba2X](3+) structural feature. The planar Ba-Xi hexagonal rings ace centered by divanadate groups in an eclipsed orientation. Edge-sharing chains of (1)(infinity)[CuO2/2(OH)(2/2)O-2/1] complement the structure. The magnetic properties are associated with the magnetic Cu2+ ions and can be described as an antiferromagnetic quasi 1D S=1/2 Heisenberg system. Confirmation is obtained from both magnetic and specific heat measurements. Furthermore, lattice dynamics are studied by DFT methods, IR, and Raman spectroscopy. (C) 2015 Elsevier Inc. All rights reserved.