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Title: A mixed phosphine sulfide/selenide structure as an instructional example for how to evaluate the quality of a model
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), C 26 H 22 P 2 S 1.13 Se 0.87 . 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 F obs 2 and F calc 2 , plots of | F obs | vs | F calc |, 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.  more » « less
Award ID(s):
2102576
PAR ID:
10429123
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Acta Crystallographica Section E Crystallographic Communications
Volume:
79
Issue:
4
ISSN:
2056-9890
Page Range / eLocation ID:
246 to 253
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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