Lanning, O. J., Habershon, Scott, Harris, K. D. M., Johnston, R. L., Kariuki, B. M., Tedesco, E. and Turner, G. W.. (2000) Definition of a 'guiding function' in global optimization: a hybrid approach combining energy and R-factor in structure solution from powder diffraction data. Chemical Physics Letters, Vol. 317 (No. 3-5). p. 296. ISSN 1873-4448

Abstract

Two global optimization problems of current interest in solid state sciences are crystal structure prediction (optimization of structure with respect to computed energy) and direct-space techniques far crystal structure solution from powder diffraction data (optimization of structure with respect to R-factor). As the energy and R-factor hypersurfaces are based on the same parameter space but have differing characteristics, there is a direct opportunity to blend these approaches together in the definition of a hybrid hypersurface. A strategy for combining R-factor and energy within a direct-space method for structure solution from powder diffraction data is proposed. Normalized energy and normalized R-factor functions are defined, and are combined using a sliding weighting function to give a hybrid figure-of-merit G, which behaves as energy when energy is high (thus using energy to guide the calculation towards energetically plausible structures) and gives increasing importance to R-factor as lower energies are approached, This concept of a 'guiding function' may be widely applicable in other global optimization problems, (C) 2000 Elsevier Science B.V, All rights reserved.

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