Analyzing diffuse scattering with supercomputers

Michels-Clark, T.M.; Lynch, T.M.; Hoffmann, C.M.; Hauser, Jürg; Weber, T.; Harrison, R.; Bürgi, Hans-Beat (2013). Analyzing diffuse scattering with supercomputers. Journal of applied crystallography, 46(6), pp. 1616-1625. Blackwell 10.1107/S0021889813025399

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Two new approaches to quantitatively analyze diffuse diffraction intensities from faulted layer stacking are reported. The parameters of a probability-based growth model are determined with two iterative global optimization methods: a genetic algorithm (GA) and particle swarm optimization (PSO). The results are compared with those from a third global optimization method, a differential evolution (DE) algorithm [Storn & Price (1997). J. Global Optim. 11, 341–359]. The algorithm efficiencies in the early and late stages of iteration are compared. The accuracy of the optimized parameters improves with increasing size of the simulated crystal volume. The wall clock time for computing quite large crystal volumes can be kept within reasonable limits by the parallel calculation of many crystals (clones) generated for each model parameter set on a super- or grid computer. The faulted layer stacking in single crystals of trigonal three-pointedstar- shaped tris(bicylco[2.1.1]hexeno)benzene molecules serves as an example for the numerical computations. Based on numerical values of seven model parameters (reference parameters), nearly noise-free reference intensities of 14 diffuse streaks were simulated from 1280 clones, each consisting of 96 000 layers (reference crystal). The parameters derived from the reference intensities with GA, PSO and DE were compared with the original reference parameters as a function of the simulated total crystal volume. The statistical distribution of structural motifs in the simulated crystals is in good agreement with that in the reference crystal. The results found with the growth model for layer stacking disorder are applicable to other disorder types and modeling techniques, Monte Carlo in particular.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry

UniBE Contributor:

Hauser, Jürg

Subjects:

500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry

ISSN:

0021-8898

Publisher:

Blackwell

Language:

English

Submitter:

Jürg Hauser

Date Deposited:

20 Aug 2014 13:40

Last Modified:

09 Dec 2014 22:41

Publisher DOI:

10.1107/S0021889813025399

Uncontrolled Keywords:

diffuse scattering, quantitative analysis, supercomputers

BORIS DOI:

10.7892/boris.58136

URI:

https://boris.unibe.ch/id/eprint/58136

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