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Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2

Fugel, Malte; Jayatilaka, Dylan; Hupf, Emanuel; Overgaard, Jacob; Hathwar, Venkatesha R.; Macchi, Piero; Turner, Michael J.; Howard, Judith A.K.; Dolomanov, Oleg V.; Puschmann, Horst; Iversen, Bo B.; Bürgi, Hans-Beat; Grabowsky, Simon

Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2 Thumbnail


Malte Fugel

Dylan Jayatilaka

Emanuel Hupf

Jacob Overgaard

Venkatesha R. Hathwar

Piero Macchi

Michael J. Turner

Oleg V. Dolomanov

Bo B. Iversen

Hans-Beat Bürgi

Simon Grabowsky


Hirshfeld atom refinement (HAR) is a novel X-ray structure refinement technique that employs aspherical atomic scattering factors obtained from stockholder partitioning of a theoretically determined tailor-made static electron density. HAR overcomes many of the known limitations of independent atom modelling (IAM), such as too short element–hydrogen distances, r(X—H), or too large atomic displacement parameters (ADPs). This study probes the accuracy and precision of anisotropic hydrogen and non-hydrogen ADPs and of r(X—H) values obtained from HAR. These quantities are compared and found to agree with those obtained from (i) accurate neutron diffraction data measured at the same temperatures as the X-ray data and (ii) multipole modelling (MM), an established alternative method for interpreting X-ray diffraction data with the help of aspherical atomic scattering factors. Results are presented for three chemically different systems: the aromatic hydro­carbon rubrene (orthorhombic 5,6,11,12-tetra­phenyl­tetracene), a co-crystal of zwitterionic betaine, imidazolium cations and picrate anions (BIPa), and the salt potassium hydrogen oxalate (KHOx). The non-hydrogen HAR-ADPs are as accurate and precise as the MM-ADPs. Both show excellent agreement with the neutron-based values and are superior to IAM-ADPs. The anisotropic hydrogen HAR-ADPs show a somewhat larger deviation from neutron-based values than the hydrogen SHADE-ADPs used in MM. Element–hydrogen bond lengths from HAR are in excellent agreement with those obtained from neutron diffraction experiments, although they are somewhat less precise. The residual density contour maps after HAR show fewer features than those after MM. Calculating the static electron density with the def2-TZVP basis set instead of the simpler def2-SVP one does not improve the refinement results significantly. All HARs were performed within the recently introduced HARt option implemented in the Olex2 program. They are easily launched inside its graphical user interface following a conventional IAM.


Fugel, M., Jayatilaka, D., Hupf, E., Overgaard, J., Hathwar, V. R., Macchi, P., …Grabowsky, S. (2018). Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2. IUCrJ, 5(1), 32-44.

Journal Article Type Article
Acceptance Date Oct 25, 2017
Online Publication Date Jan 1, 2018
Publication Date Jan 1, 2018
Deposit Date Jan 25, 2018
Publicly Available Date Jan 25, 2018
Journal IUCrJ
Publisher International Union of Crystallography
Peer Reviewed Peer Reviewed
Volume 5
Issue 1
Pages 32-44


Published Journal Article (1.5 Mb)

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Copyright Statement
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

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