The use of the serial-correlations concept in the figure-of-merit function for powder diffraction profile fitting

A new figure-of-merit function for full-profile fitting of powder patterns has been tested using the neutron diffraction data file for PbSO₄, distributed during the first part of the Rietveld Refinement Round Robin organized by the Commission on Powder Diffraction of the International Union of Crystallography, and the X-ray diffraction data file for Ca₅(PO₄)₃F, used as the test case for the DBW Rietveld refinement computer programs. The function takes into account the systematic behaviour of the residuals in the final fit owing to local serial correlations. The problems in current structure-refinement techniques are discussed and possible methods for their solution are proposed.