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X‐ray constrained wavefunctions based on Hirshfeld atoms. II. Reproducibility of electron densities in crystals of α‐oxalic acid dihydrate
Author(s) -
Davidson Max L.,
Grabowsky Simon,
Jayatilaka Dylan
Publication year - 2022
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520622004103
Subject(s) - extrapolation , wave function , reproducibility , electron density , electron , oxalic acid , chemistry , atom (system on chip) , mathematics , series (stratigraphy) , mathematical analysis , quantum mechanics , physics , statistics , computer science , inorganic chemistry , paleontology , biology , embedded system
The Hirshfeld atom‐based X‐ray constrained wavefunction fitting (HA‐XCW) procedure is tested for its reproducibility, and the information content of the fitted wavefunction is critically assessed. Fourteen different α‐oxalic acid dihydrate data sets are used for this purpose, and the first joint fitting to 12 of these data sets is reported. There are systematic features in the electron density obtained from all data sets which agree with higher level benchmark calculations, but there are also many other strong systematic features which disagree with the reference calculations, most notably those associated with the electron density near the nuclei. To enhance reproducibility, three new protocols are described and tested to address the halting problem of XCW fitting, namely: an empirical power‐function method, which is useful for estimating the accuracy of the structure factor uncertainties; an asymptotic extrapolation method based on ideas from density functional theory; and a `conservative method' whereby the smallest value of the regularization parameter is chosen from a series of data sets, or subsets.