A Synchrotron Powder Diffraction Study of Na-LTA

The charge density distribution of Na-LTA is obtained by the Maximum Entropy Method (MEM) using synchrotron powder data. In the MEM map, all the components; framework, cations and absorbed water molecules, are all clearly shown even if the site occupation is very low, say less than 10%. A powder diffraction experiment is carried out by the transmission geometry with Imaging Plate (IP) detector at BL-6A2, PR In the analysis, a new method which is a iterative use of Rietveld refinement and MEM is applied in order to improve a structure model used in Rietveld refinement. An initial structure model used in Rietveld is just simple framework only. In the first Rietveld refinement, the agreement factor, RI, was very bad, i.e.37.4%. Following MEM analysis, however, gives the key information of how to improve next structure model for Rietveld refinement. Improvement of the structure model by the present method eventually lead to RI to be as low as 5.2%, which proves a great success of the method. The present method may lead a drastic change of structural studies of zeolite compounds when it is applied to high resolution and high intensity synchrotron powder data.