Structure cristalline d'une nouvelle variete de pyrophosphate de nickel: Ni2P2O7

Three forms of nickel pyrophosphate are already known. A new form was prepared and structure determined by Patterson method. σ Ni2P2O7 is monoclinic with a = 5.212(3), b = 9.913(5), c = 4.475(3) Å, β = 97°46(10). The space group is P21a. The structure was refined until a R value of 0.041 for 1374 independent reflexions. Framework is built with P2O7 groups and NiO6 octaedra. The P-O-P bonding is linear. σ Ni2P2O7 is isotypic with the pyrosilicate Er2Si2O7.