A benchmark method for global optimization problems in structure determination from powder diffraction data

K. Shankland, A. J. Markvardsen, C. Rowlatt, N. Shankland, W. I. F. David

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Quasi-Newton–Raphson minimization and conjugate gradient minimization have been used to solve the crystal structures of famotidine form B and capsaicin from X-ray powder diffraction data and characterize the χ2 agreement surfaces. One million quasi-Newton–Raphson minimizations found the famotidine global minimum with a frequency of ca 1 in 5000 and the capsaicin global minimum with a frequency of ca 1 in 10 000. These results, which are corroborated by conjugate gradient minimization, demonstrate the existence of numerous pathways from some of the highest points on these χ2 agreement surfaces to the respective global minima, which are passable using only downhill moves. This important observation has significant ramifications for the development of improved structure determination algorithms.
Original languageEnglish
Pages (from-to)401-406
Number of pages6
JournalJournal of Applied Crystallography
Volume43
Issue numberPart 3
DOIs
Publication statusPublished - 1 Jun 2010

Keywords

  • structure determination
  • powder diffraction data
  • conjugate gradient minimisation
  • quasi-Newton minimisation
  • global optimisation

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