Rietveld refinements results, using Rigaku's Ultima IV multipurpose diffraction system, were obtained from a solid rock chunk sample (Figures 1 and 2) composed of six mineral phases. The XRD data was collected in both the parallel and para-focusing beam geometry.
As shown in Figure 3, the rock sample has a highly uneven surface causing the focusing beam data to have both inaccurate peak positions and lower than expected intensities. The shifted peak positions generally arise from a number of displacement errors associated with the sample morphology. Roughness, transparency, and curvature all contribute to the error.
The use of parallel beam geometry completely circumvents these errors since no focusing is required. The parallel beam data provides accurate peak positions and better intensities as shown in Figure 3. The comparative Rietveld refinement results are shown in Figure 4 and Table 1. It can be seen that better results were obtained with the parallel beam data.