A mixed phosphine sulfide/selenide structure as an instructional example for how to evaluate the quality of a model

Sean Parkin, Jeremy Cunningham, Brian Rawls, John E. Bender, Richard J. Staples, Shannon M. Biros

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


This paper compares variations on a structure model derived from an X-ray diffraction data set from a solid solution of chalcogenide derivatives of cis-1,2-bis(diphenylphosphanyl)ethylene, namely, 1,2-(ethene-1,2-diyl)bis(diphenyl-phoshpine sulfide/selenide), C26H22P2S1.13Se0.87. A sequence of processes are presented to ascertain the composition of the crystal, along with strategies for which aspects of the model to inspect to ensure a chemically and crystallographically realistic structure. Criteria include mis-matches between Fobs2 and Fcalc2 , plots of |Fobs| vs |Fcalc|, residual electron density, checkCIF alerts, pitfalls of the OMIT command used to suppress ill-fitting data, comparative size of displacement ellipsoids, and critical inspection of interatomic distances. Since the structure is quite small, solves easily, and presents a number of readily expressible refinement concepts, we feel that it would make a straightforward and concise instructional piece for students learning how to determine if their model provides the best fit for the data and show students how to critically assess their structures.

Original languageEnglish
Pages (from-to)246-253
Number of pages8
JournalActa Crystallographica Section E: Crystallographic Communications
Issue numberPt 4
StatePublished - Mar 28 2023

Bibliographical note

Publisher Copyright:
© 2023 International Union of Crystallography. All rights reserved.


  • F vs F
  • OMIT command
  • checkCIF alerts
  • crystal structure
  • disordered electron density
  • displacement ellipsoids
  • outliers
  • solid solution
  • standard interatomic distances

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics


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