The crystal structure of wooldridgeite, Na2CaCu2+2(P2O7)2(H2O)10, a novel copper pyrophosphate mineral

The crystal structure of wooldridgeite, Na-2 Ca Cu-2(2+) (P2O7)(2) (H2O)(10), orthorhombic, a 11.938(1), b 32.854(2), c 11.017(1) Angstrom, V 4321.2(8) Angstrom(3), Z = 8, was solved by direct methods in the space group Fdd2 and refined by a full-matrix least-squares method to an R index of 3.4% for 1649 observed (\ F-o \ > 5 sigma \ F-o \) reflections. There are two distinct P sites, each tetrahedrally coordinated by four O atoms; the resulting phosphate tetrahedra link through a common anion to form a [P2O7] group. There is one unique Cu site octahedrally coordinated by four O atoms and two (H2O) groups, with typical Jahn-Teller distortion [1.94 less than or equal to Cu (O, H2O) less than or equal to 3.39 Angstrom]. There is one unique Ca site octahedrally coordinated by four O atoms and two (H2O) groups, and one unique Na site octahedrally coordinated by two O atoms and four (H2O) groups. The (Cu phi(6)) (phi: unspecified anion) octahedra each share two trans vertices to form a [Cu phi(5)] chain of corner-sharing octahedra that is decorated with flanking (P2O7) groups to form a [Cu(P2O7)(H2O)] chain. These chains are arranged parallel in layers orthogonal to [010], and the chains in adjacent layers are mutually orthogonal. This array of chains is held together by interstitial Ca and Na, and a network of H bonds.