RIETVELD ANALYSIS OF POWDER DIFFRACTION PATTERNS

Rietveld analysis is a means of revealing the detailed structure and c omposition of a polycrystalline sample using X-ray or neutron powder d iffraction data. A starting model of the material is used to calculate an entire diffraction pattern. The model parameters (and hence the ca lculated pattern) are refined by the method of least squares until a g ood fit to the observed data is obtained. Depending on the nature of t he problem under study, the method can provide accurate lattice parame ters, atom cc-ordinates, thermal parameters, occupancy factors, partic le size and micro-strain estimates. This work reviews the essential el ements of the technique, gives practical examples in the solution of M aterials Science problems and then addresses practical aspects of the techniques use which often deter non-crystallographers from making use of it.