Rietveld refinement of geological material: pushing the envelope

In contrast to profile-fitting procedures that use isolated integrated peak intensities, the Rietveld Refinement method fits the entire powder diffraction pattern. This method overcomes the problem of severe peak overlap especially in multiphase materials and complex structures with low symmetry, allowing users to obtain better information from compact powder diffraction patterns.

Figure 1 shows the diffraction pattern of one such geological sample containing thirteen mineral phases collected on the Rigaku Ultima IV. Two of the phases were below 0.1 weight percent in the total mixture. Figures 2 and 3 show the Rietveld refinement using the Whole Pattern Fitting (WPF) module in Jade for this sample. Quantitative information (Figure 4) was obtained for the eleven phases, four of which were trace phases under 1.0 weight percent of the total mixture .

For even more complex mixtures Jade's WPF module can include up to ten amorphous peaks and sixteen crystalline phases in the refinement.