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Article Dans Une Revue Acta Crystallographica Section A : Foundations and Advances [2014-...] Année : 2023

Introduction of a weighting scheme for the X-ray restrained wavefunction approach: advantages and drawbacks

Résumé

In a quite recent study (Genoni, Dos Santos et al., 2017), it was observed that the X-ray restrained wavefunction (XRW) approach allows a more efficient and larger capture of electron correlation effects on the electron density if high-angle reflections are not considered in the calculations. This was due to the occurrence of two concomitant effects when one uses theoretical X-ray diffraction data corresponding to a single-molecule electron density in a large unit-cell: i) the high-angle reflections are generally much more numerous than the low- and medium-angle ones and ii) they are already very well-described at unrestrained level. Nevertheless, since high-angle data also contain important information that should not be disregarded, their complete neglect is not advisable. For this reason, based on the results of the previous investigation, in this work we have introduced a weighting scheme for XRW calculations to up-weight the contribution of low- and medium-angle reflections, and, at the same time, to reasonably down-weight the importance of the high-angle data. The proposed strategy was tested through XRW computations with both theoretical and experimental structure factor amplitudes. The tests have shown that the new weighting scheme optimally works if it is applied with theoretically generated X-ray diffraction data, while it is not advantageous when traditional experimental X-ray diffraction data (even of very high resolution) are employed. This also led to the conclusion that the use of a specific external parameter λ_J for each resolution range might not be a suitable strategy to be adopted in XRW calculations exploiting experimental X-ray data as restraints.
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Dates et versions

hal-03870539 , version 1 (24-11-2022)

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Giovanni Macetti, Alessandro Genoni. Introduction of a weighting scheme for the X-ray restrained wavefunction approach: advantages and drawbacks. Acta Crystallographica Section A : Foundations and Advances [2014-..], 2023, 79 (1), ⟨10.1107/S2053273322010221⟩. ⟨hal-03870539⟩
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