Speaker: Ben Ebel, Molecular Functional Materials, RWTH Aachen University.

Topic:
Today, the continuous improvement of diffractometers and data reduction software routinely allows the collection of high-quality data sets, leading to crystallographic models which are often limited by the neglection of chemical features (e.g. residual desity on chemical bonds) through the use of non-interacting, spherically averaged atomic form factors, also referred to as the Independent Atom Model (IAM). With the increase in computing power, more accurate non-spherical form factors can be calculated for example using a quantum mechanical software and the Hirshfeld partitioning scheme^[1]. This method, called Hirshfeld Atom Refinement (HAR)^[2,3], has been implemented into Olex2^[4] as the NoSpherA2^[5] software, which automatically handles all of the necessary processes. Nevertheless, the large amounts of levels of theory a user can choose for the model can be overwhelming to beginners and the computational cost can be very large depending on the size/number of electrons of the compound. Here, we present the implementation of Grimme’s pTB^[6] software into NoSpherA2, a semi-empirical tight-binding method developed to accurately reproduce the electron density of a chemical system in a fraction of the time of a DFT method of the same level and show a few examples comparing the models obtained from the different methods.

[1] F. L. Hirshfeld, Israel Journal of Chemistry 1977, 16, 198–201.
[2] S. C. Capelli, H.-B. Bürgi, B. Dittrich, S. Grabowsky, D. Jayatilaka, IUCrJ 2014, 1, 361–379.
[3] D. Jayatilaka, B. Dittrich, Acta Cryst A 2008, 64, 383–393.
[4] O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H. Puschmann, J Appl Crystallogr 2009, 42, 339–341.
[5] F. Kleemiss, O. V. Dolomanov, M. Bodensteiner, N. Peyerimhoff, L. Midgley, L. J. Bourhis, A. Genoni, L. A. Malaspina, D. Jayatilaka, J. L. Spencer, F. White, B. Grundkötter-Stock, S. Steinhauer, D. Lentz, H. Puschmann, S. Grabowsky, Chem. Sci. 2021, 12, 1675–1692.
[6] S. Grimme, M. Müller, A. Hansen, The Journal of Chemical Physics 2023, 158, 124111.

Series: STOE User Talks 2025/2026

Time: 37 min.