The Rietveld J. Appl. Cryst. (1969), 2, 65–71 method of structure refinement from powder diffraction patterns is widely used with neutron data and increasingly so with X-ray data. A computer program for the application of the method with X-ray data, or with neutron nuclear scattering data, has been written ab initio in an effort to make it versatile, user oriented, portable, convenient, and largely self-contained yet reasonably comprehensive. It is of modular construction to facilitate user-desired modifications, one of which may be additions to the choice of four profile functions now included. The program accommodates either one or two wavelengths (e.g. α1 and α2 or λ and λ/2). It permits simultaneous refinement of the structures of two phases and the background.
Wiles et al. (Wed,) studied this question.