CRYSTAL CHEMISTRY OF SELENATES WITH MINERAL-LIKE STRUCTURES. IV. CRYSTAL STRUCTURE OF Zn(SeO4)(H2O)2, A NEW COMPOUND WITH A MIXED FRAMEWORK OF THE VARISCITE TYPE

Abstract

The crystal structure of a new compound Zn(SeO4)(H2O)2 (orthorhombic, Pbca, a = 9.0411(13), b = 10.246(2), c = 10.3318(15) Å, V = 957.1(3) Å3) has been solved by direct methods and refined to R 1 = 0.033 on the basis of 1076 observed reflections with |F hkl | ≥ 4σ|F hkl |. The structure contains one independent Zn2+ cation coordinated by two water molecules and four oxygen atoms of selenate group. The only independent (SeO4)2− tetrahedral oxoanion is tetradentate, sharing its corners with four adjacent [Zn2+O2(H2O4)]2+ octahedrons. The structure can be described as consisting of heteropolyhedral sheets parallel to the (001) plane and linked together into a three-dimensional network. The compound belongs to the variscite structure type and is the first structurally characterized selenate of this group.