A mixed phosphine sulfide/selenide structure as an instructional example for how to evaluate the quality of a model
| Autor: | Sean Parkin, Jeremy Cunningham, Brian Rawls, John E. Bender, Richard J. Staples, Shannon M. Biros |
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| Jazyk: | angličtina |
| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | Acta Crystallographica Section E: Crystallographic Communications, Vol 79, Iss 4, Pp 246-253 (2023) |
| Druh dokumentu: | article |
| ISSN: | 2056-9890 20569890 |
| DOI: | 10.1107/S2056989023002700 |
| Popis: | 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(diphenylphoshpine 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. |
| Databáze: | Directory of Open Access Journals |
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