Chapter 7 The rietveld method and its applications to synchrotron X-ray powder data

Abstract

Publisher Summary The Rietveld method is a technique for refining structure and lattice parameters directly from whole X-ray or neutron powder diffraction patterns without separating peaks contained in them. The Rietveld method substantially contains the following data-processing procedures: (i) separation of overlapping peaks in diffraction patterns, (ii) separation of Kα I and Kα 2 peaks when using characteristic X-rays, (iii) background subtraction, (iv) refinement of lattice parameters, (v) refinement of structure parameters (fractional coordinates, occupation factors, and thermal-displacement parameters), (vi) correction of preferred orientation, (vii) determination of mixing ratios, (viii) identification of impurity peaks, (ix) indexing of reflections, and (x) determination of integrated intensities, full-widths at half-maximum intensities (FWHM), and peak positions. The Rietveld method, in which these complex calculations are executed simultaneously, is an exquisite technique for the analysis of powder-diffraction data. The Rietveld method is widely applicable to metals, inorganic compounds, and organic compounds of low molecular weights only if they are crystalline.