XRD analysis with whole pattern fitting refinement
Invented by Hugo Rietveld, Whole Pattern Fitting Structure Refinement is now widely accepted to be an exceptionally valuable method for structural analysis of nearly all classes of crystalline materials not available as single crystals. For the X-ray diffraction (XRD) technique, Rietveld Analysis is analogous to the Fundamental Parameters technique for X-ray fluorescence (XRF).
This software approach refines various metrics—including lattice parameters, peak width and shape, and preferred orientation—to derive a calculated diffraction pattern. Once the derived pattern is nearly identical to an unknown sample data, various properties pertaining to that sample can be obtained including: accurate quantitative information, crystallite size, and site occupancy factors. The process of refining the pattern is computationally intensive, requiring several minutes to calculate results for a multi-component mixture. Rietveld Analysis has the advantage, over conventional quantitative methods, that no standards are required to achieve accurate results to within ±1%. Before this advance, an accurate and standardless quantitative phase analysis of complex materials using powder diffraction was almost impossible.