Disodium calcium dinickel(II) bis-[diphosphate(V)] decahydrate

In the title compound, Na(2)CaNi(2)(P(2)O(7))(2)(H(2)O)(10), there are two distinct P-atom sites, each tetra-hedrally coordinated by four O atoms. The resulting phosphate tetra-hedra link through a common O atom, forming a [P(2)O(7)](4-) diphosphate unit. The Ni-O coordination is square pyramidal with four O atoms from two diphosphate groups in equatorial positions and the vertex occupied by a water O atom. The (P(2)O(7))(H(2)O) units link the Ni atoms, forming a chain of pyramids and tetra-hedra. As a result of the d-glide and twofold-axis symmetry of space group Fdd2, the chains propagate along [101] and [10], and chains in adjacent layers are mutually orthogonal. The Ca cation, located on a rotation axis, and the Na cation are each octa-hedrally coordinated by four O atoms and two waters. The Ni-chain arrangement is stabilized by Ca and Na coordination and a network of O-H⋯O hydrogen bonds.