Li6P6O18: X-Ray Powder Structure Determination of Lithium Cyclohexaphosphate.

Abstract Preparation, characterization by X-ray diffraction, IR absorption, DTATG analysis, and ab-initio crystal structure determination are reported for anhydrous lithium cyclohexaphosphate Li6P6O18. It crystallizes in a monoclinic cell (space group P21/n No14, Z=2) with a = 7.9911(3)A, b = 17.0319(6)A, c = 5.3208(2)A and β = 99.433(1)°. X-ray powder diffraction data were fitted by Rietveld method leading to RBragg = 0.034. The crystal structure of Li6P6O18 is built up from P6O18 ring anions, with 1 internal symmetry. Six lithium coordination polyhedra (two pseudo square pyramids and four tetrahedra) share common edges and corners as to form Li6O16 groups. These cationic groups build up a layer in the (1 0 1¯) plane showing large distorted hexagonal tunnels and interconnect the P6O18 rings in a three dimensional way.