BaCo2(AsO4)2

Abstract

Suitable single crystals of the title compound, barium dicobalt(II) bis[orthoarsenate(V)], were prepared under hydrothermal conditions. This phase belongs to a series of compounds with general formula AM 2(XO4)2, where A = alkaline earth metal, M = Mg or a divalent first-row transition element, and X = P, As or V. BaCo2(AsO4)2 is isotypic with BaNi2(XO4)2 (X = P, V or As) and is characterized by brucite-like sheets of edge-sharing CoO6 octahedra (3 symmetry) parallel to (001), with one-third of the octahedral positions being vacant. The sheets are capped above and below by AsO4 tetrahedra (3 symmetry) and are interconnected by distorted BaO12 cuboctahedra (\overline{3} symmetry).