Crystal structure of KNaCuP(2)O(7), a new member of the diphosphate family.

Potassium sodium copper(II) diphosphate(V), KNaCuP(2)O(7), was synthesized by solid-state reactions. It crystallizes in the α-Na(2)CuP(2)O(7) structure type in space group P2(1)/n. In the crystal, CuO(5) square-pyramids are linked to nearly eclipsed P(2)O(7) groups by sharing corners to build up corrugated layers with composition [CuP(2)O(7)](2-) that extend parallel to (010). The K(+) and Na(+) cations reside in the inter-layer space and are connected to nine and seven O atoms, respectively. The structural model was validated by bond-valence-sum (BVS) and charge-distribution (CHARDI) analysis.