Global Rietveld Refinement.

Global optimisation methods of structure determination from powder diffraction data have risen to prominence in a relatively short space of time and they now constitute a key approach in the examination of polycrystalline molecular organic materials. A correctly formulated global optimisation approach may be regarded as a "global Rietveld refinement" that is capable of delivering accurate crystal structures from high-quality powder diffraction data. This paper focuses on how accuracy at all stages of a powder diffraction experiment impacts upon the overall structure solution process and particular attention is paid to assessing the degree of accuracy with which structures are returned from the global optimisation process.