Definition of a 'guiding function' in global optimization:: a hybrid approach combining energy and R-factor in structure solution from powder diffraction data

被引:39
作者
Lanning, OJ [1 ]
Habershon, S [1 ]
Harris, KDM [1 ]
Johnston, RL [1 ]
Kariuki, BM [1 ]
Tedesco, E [1 ]
Turner, GW [1 ]
机构
[1] Univ Birmingham, Sch Chem, Birmingham B15 2TT, W Midlands, England
基金
英国工程与自然科学研究理事会;
关键词
D O I
10.1016/S0009-2614(99)01366-4
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
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.
引用
收藏
页码:296 / 303
页数:8
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