Refinement of the structure of LiMnPO 4

Abstract

The least-squares technique applied to three-dimensional X-ray diffraction data has been used to refine the structure of LiMnPO~. The crystal belongs to space group D~g-Pmnb; the unit cell with a=6.10+0.02, b=10.46+0.03, c=4-744+0.010 Jk contains four formula tmits. The structure is closely related to that of olivine (Mg2SiO~). It consists of discrete PO4 tetrahedral complexes and highly distorted oxygen octahedra about the Li + and Mn 2+ ions. The average P-O distance is 1.54 A with no significant differences among the three non-equivalent P-O distances. The PO4 tetrahedron is not regular, however, there being two significantly different sets of O-O distances or O-P-O angles. For this structure, neglect of off-diagonal terms of the normal equations matrix of the least-squares calculation does not significantly affect the results. Furthermore the least-squares calculation with use of only the [001], [010], and [100] zonal data and neglect of the off-diagonal terms of the normal equations matrix gives results differing in only a minor way from those obtained by use of three-dimensional data and inclusion of the off-diagonal terms of the normal equations matrix.