Dilithium barium diphosphate.

The crystal structure of the novel title diphosphate, Li2BaP2O7, exists with a three-dimensional lattice composed of BaO9 polyhedra linked to corner- and edge-sharing P2O7 diphos­phate groups, forming layers parallel to the (010) plane, the layers being linked by P—O—Ba bridges. Tunnels thus created between the layers are occupied by Li+ cations, two of which lie on twofold axes.