Redetermination of the low-temperature polymorph of Li 2MnSiO4 from single-crystal X-ray data

Abstract

Crystals of dilithium manganese(II) silicate were grown under high-temperature hydro-thermal conditions in the system LiOH - MnO2 - SiO2. The title compound crystallizes in the ΒII-Li 3PO4 structure type. The coordination polyhedra of all cations are slightly distorted tetra-hedra (m symmetry for MnO4 and SiO4), which are linked by corner-sharing to each other. The vertices of the tetra-hedra point to the same direction perpendicular to the distorted hexa-gonal close-packed (hcp) array of O atoms within which half of the tetra-hedral voids are occupied by cations. In comparison with the previous refinement from powder X-ray data [Dominko et al. (2006). Electrochem. Commun. 8, 217-222], the present reinvestigation from single-crystal X-ray data allows a more precise determination of the distribution of the Li+ and Mn2+ cations, giving a perfectly site-ordered structure model for both Li+ and Mn2+.