Hirshfeld atom refinement and dynamical refinement of hexagonal ice structure from electron diffraction data.

Autor: Chodkiewicz ML; Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warszawa, Warszawa 02-089, Poland., Olech B; Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warszawa, Warszawa 02-089, Poland., Jha KK; Centre of New Technologies, University of Warsaw, S. Banacha 2c, Warsaw 02-097, Poland., Dominiak PM; Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warszawa, Warszawa 02-089, Poland., Woźniak K; Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury 101, Warszawa, Warszawa 02-089, Poland.
Jazyk: angličtina
Zdroj: IUCrJ [IUCrJ] 2024 Sep 01; Vol. 11 (Pt 5), pp. 730-736. Date of Electronic Publication: 2024 Sep 01.
DOI: 10.1107/S2052252524006808
Abstrakt: Reaching beyond the commonly used spherical atomic electron density model allows one to greatly improve the accuracy of hydrogen atom structural parameters derived from X-ray data. However, the effects of atomic asphericity are less explored for electron diffraction data. In this work, Hirshfeld atom refinement (HAR), a method that uses an accurate description of electron density by quantum mechanical calculation for a system of interest, was applied for the first time to the kinematical refinement of electron diffraction data. This approach was applied here to derive the structure of ordinary hexagonal ice (I h ). The effect of introducing HAR is much less noticeable than in the case of X-ray refinement and it is largely overshadowed by dynamical scattering effects. It led to only a slight change in the O-H bond lengths (shortening by 0.01 Å) compared with the independent atom model (IAM). The average absolute differences in O-H bond lengths between the kinematical refinements and the reference neutron structure were much larger: 0.044 for IAM and 0.046 Å for HAR. The refinement results changed considerably when dynamical scattering effects were modelled - with extinction correction or with dynamical refinement. The latter led to an improvement of the O-H bond length accuracy to 0.021 Å on average (with IAM refinement). Though there is a potential for deriving more accurate structures using HAR for electron diffraction, modelling of dynamical scattering effects seems to be a necessary step to achieve this. However, at present there is no software to support both HAR and dynamical refinement.
(open access.)
Databáze: MEDLINE
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