Synthesis, crystal structure and vibrational spectra of a new form of diphosphate NaLaP2O7

Synthesis and complete structural characterization by X-ray diffraction, Raman and infrared spectroscopy are given for a new form of NaLaP2O7 diphosphate. This compound crystallizes in the orthorhombic Pnma space group with the following unit cell dimensions: a = 8.645(2), b = 5.317(1), c = 12.737(2) Angstrom, V = 5 85.5(2) Angstrom(3), Z = 4. The single crystal structure was solved from 906 independent reflections (F-o(2) greater than or equal to 2sigma(F-o(2))) with final R-1(F-2) = 0.0364 and R-W(F-2) = 0.0918, refined with 62 parameters. In this structure the P2O7 groups are connected to the LaO9 polyhedra by edge-sharing to form a three-dimensional framework. The sodium cations are coordinated by nine oxygen atoms and build ribbons of NaO9 polyhedra running parallel to the b-direction. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared and Raman spectra. (C) 2004 Elsevier Ltd. All rights reserved.