β-Xenophyllite-type Na₄Li_0.62Co_5.67Al_0.71(AsO₄)₆

The title compound, tetrasodium lithium cobalt aluminium hexa­(orthoarsenate), was synthesized by a solid state reaction route. In the crystal structure, Co²⁺ ions are partially substituted by Al³⁺ in an octa­hedral environment [M1 with site symmetry 2/m; occupancy ratio Co:Al = 0.286 (10):0.714 (10)]. The charge compensation is ensured by Li⁺ cations sharing a tetra­hedral site with Co²⁺ ions [M2 with site symmetry 2; occupancy ratio Co:Li = 0.690 (5):0.310 (5)]. The anionic unit is formed by two octa­hedra and three tetra­hedra linked only by corners. The CoM1M2As₂O₁₉ units associate to an open three-dimensional framework containing tunnels propagating along the a-axis direction. One Na⁺ cation is located in the periphery of the tunnels while the other two are situated in the centres: all Na⁺ cations exhibit half-occupancy. The structure of the studied material is compared with those of various related minerals reported in the literature.