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

Abstract Synthesis and complete structural characterization by X-ray diffraction, Raman and infrared spectroscopy are given for a new form of NaLaP 2 O 7 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) A, V = 585.5(2) A 3 , Z = 4. The single crystal structure was solved from 906 independent reflections ( F o 2 ≥ 2 σ ( 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 P 2 O 7 groups are connected to the LaO 9 polyhedra by edge-sharing to form a three-dimensional framework. The sodium cations are coordinated by nine oxygen atoms and build ribbons of NaO 9 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.