LiCo₂As₃O₁₀: une nouvelle structure à tunnels inter­connectés

The title compound, lithium dicobalt(II) triarsenate, LiCo₂As₃O₁₀, was synthesized by a solid-state reaction. The As atoms and four out of seven O atoms lie on special positions, all with site symmetry m. The Li atoms are disordered over two independent special (site symmetry -1) and general positions with occupancies of 0.54 (7) and 0.23 (4), respectively. The structure model is supported by bond-valence-sum (BVS) and charge-distribution (CHARDI) methods. The structure can be described as a three-dimensional framework constructed from bi-octahedral Co₂O₁₀ dimers edge-connected to As₃O₁₀ groups. It delimits two sets of tunnels, running parallel to the a and b axes, the latter being the larger. The Li⁺ ions are located within the inter­sections of the tunnels. The possible motion of the alkali cations has been investigated by means of the BVS model. This simulation shows that the Li⁺ motion appears to be easier mainly along the b-axis direction and that this material may possess inter­esting conduction properties.