Electron density distribution and crystal structure of lithium barium silicate, Li2BaSiO4

Abstract

Crystal structure of Li2BaSiO4was reinvestigated by laboratory X-ray powder diffraction. The title compound was hexagonal with space groupP63cm,Z=6, unit-cell dimensionsa=0.810 408(2) nm,c=1.060 829(4) nm, andV=0.603 370(3) nm3. The initial structural model was successfully derived by the direct methods and further refined by the Rietveld method, with the anisotropic atomic displacement parameters being assigned for all atoms. The reliability indices calculated from the Rietveld refinement wereRwp=6.72%,S=1.17,Rp=5.06%,RB=1.86%, andRF=0.98%. The maximum-entropy method-based pattern fitting (MPF) method was used to confirm the validity of the structural model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The final reliability indices calculated from MPF wereRwp=6.74%,S=1.17,Rp=5.10%,RB=1.49%, andRF=0.69%. Atomic arrangements of the final structural model were in excellent agreement with the three-dimensional electron-density distributions determined by MPF.