Application of a Genetic Algorithm in structure determination from powder diffraction data
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Colleges, School and Institutes
- University of Birmingham
This paper describes the development of a Genetic Algorithm for solving crystal structures directly from powder diffraction data. A number of examples are given to illustrate the application of this approach for the structure determination of molecular crystals. Our approach adopts the direct-space philosophy for structure solution from powder diffraction data, in which trial structures are generated independently of the experimental diffraction data and the quality of each trial structure is assessed by comparing the calculated and experimental powder diffraction patterns using the weighted profile R-factor, Rwp. The use of the profile R-factor in this approach implicitly takes care of the overlap of peaks in the powder diffraction pattern, and avoids the need to extract the intensities of individual reflections from the experimental powder diffraction data. In our Genetic Algorithm, a population of trial crystal structures is allowed to evolve subject to well-defined rules governing mating, mutation and natural selection, and the fitness of each structure is defined as a function of Rwp. The aim is to find the minimum value of Rwp, which corresponds to the best structure solution.
|Number of pages||13|
|Publication status||Published - 1 Dec 1998|