β-Xenophyllite-type Na(4)Li(0.62)Co(5.67)Al(0.71)(AsO(4))(6)

The title compound, tetrasodium lithium cobalt aluminium hexa­(orthoarsenate), was synthesized by a solid state reaction route. In the crystal structure, Co(2+) ions are partially substituted by Al(3+) 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 Co(2+) 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 CoM1M2As(2)O(19) 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.