Crystal structure of silver strontium copper orthophosphate, AgSr4Cu4.5(PO4)6

Crystals of the new compound, AgSr 4 Cu 4.5 (PO 4 ) 6 , were grown successfully by the hydrothermal process. The asymmetric unit of the crystal structure of the title compound contains 40 independent atoms (4 Sr, 4.5 Cu, 1 Ag, 6 P and 24 O), which are all in general positions except for one Cu atom, which is located on an inversion centre. The Cu atoms are arranged in CuO n ( n = 4 or 5) polyhedra, linked through common oxygen corners to build a rigid three-dimensional motif. The connection of these copper units is assured by PO 4 tetrahedra. This arrangement allows the construction of layers extending parallel to the (100) plane and hosts suitable cavities in which Ag + and Sr 2+ cations are located. The crystal-structure cohesion is ensured by ionic bonds between the silver and strontium cations and the oxygen anions belonging to two adjacent sheets. Charge-distribution analysis and bond-valence-sum calculations were used to validate the structural model.