Density functional calculations and analysis of the crystal structure of Pb2 P2 O7

Density functional calculations of the atomic coordinates in crsytalline lead pyrophosphate (Pb2 P2 O7) are reported. These calculations yield atomic positions differing from a prior x-ray refinement by up to 0.2Å. The main difference is a change in the orientation of the (P2 O7) 4- units to bring certain O ions closer to Pb. An analysis of the resulting structure in terms of pair distribution functions is presented. These show that the most significant changes are in the local Pb coordination. The electronic structure is not significantly affected by the change in crystal structure.