Abstract
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 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.