Feb 5 2025

CDAC Webinar- “Quantum Crystallography” with Prof. Krzysztof Wozniak (University of Warsaw)

CDAC Webinar

February 5, 2025

1:00 PM - 2:00 PM

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https://uic.zoom.us/j/99098590328?pwd=Qkxia2ROdXVvSHRNUGdNaHN1Wjlodz09

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“Quantum Crystallography"
Krzysztof Wozniak
Department of Chemistry
University of Warsaw, Poland

Abstract:

This is quite a paradox: more than a century after the introduction of the spherical Independent Atom Model (IAM, 1914 [1]) of atomic electron density, 99.7% of the approximately 2.0 million known crystal structures are still refined using the IAM, despite its severe methodological deficiencies. Far better results can be obtained by applying new approaches in Quantum Crystallography (QCr), which utilize aspherical atomic scattering factors. In short, QCr represents crystallography beyond IAM. Quantum Crystallography provides structural X-ray diffraction results whose quality is comparable to those obtained from neutron diffraction studies. Additionally, QCr allows for the determination of numerous electronic parameters that characterize the electron density distribution—parameters not obtained in routine structural studies.

I will present a general overview of Quantum Crystallography, including details of aspherical Hansen-Coppens [2] pseudoatom refinement of electron density, particularly in the case of minerals, and the key ideas behind Hirshfeld Atom refinement. My lecture will be complemented by several examples of our QCr studies [3-9], including: (1) QCr studies and comparison of results for multiple hydrated oxalic acid structures, (2) multipolar refinement of electron density in minerals, including minerals under pressure and studies of phase transitions in minerals, (3) Hirshfeld Atom Refinement (HAR) of ice structures against X-ray, electron diffraction, and neutron diffraction data, (4) HAR refinement of H-atom positions in small molecule organic compounds and hydrides, and, time permitting, additional examples of QCr results.

A century after the Braggs, it is now possible to obtain H-atom positions from X-ray diffraction studies that are as reliable as those from neutron diffraction. It is also possible to determine experimentally reliable positions of H-atoms in the close vicinity of very heavy atoms, study small redistributions of electron density in minerals and their phase transitions under pressure, and estimate the consequences of relativistic effects, or electron correlation, using X-ray diffraction data. Thus, users of X-ray crystallography can achieve far better results than simply refining a poor IAM model against precise, accurate, and often expensive diffractometer, synchrotron, or XFEL X-ray data. QCr approaches can also improve the quality of macromolecular studies, powder X-ray diffraction results, pair distribution functions (PDF), XANES, EXAFS, CryoEM, electron diffraction, and more. As a result, by developing and applying QCr, one can enhance scientific outcomes and stimulate progress in all fields of science, technology, medicine and other fields that utilize structural, thermal, and electron density information.

[1] A.H. Compton, Nature., 95, (1915) pp. 343-344.

[2] N. K. Hansen, & P. Coppens, Acta Cryst., A34, (1978) 909–921.

[3] M. Woińska, S. Grabowsky, P. M. Dominiak, K. Woźniak, D. Jayatilaka, Science Advances, 2 No. 5 (2016) e1600192, DOI: 10.1126/sciadv.1600192

[4] W. F. Sanjuan-Szklarz, M. Woińska, S. Domagała, P. M. Dominiak, S. Grabowsky, D. Jayatilaka, M. Gutmann, K. Woźniak, IUCRJ, 7(5) (2020) 920-933, https://doi.org/10.1107/S2052252520010441

[5] M. L. Chodkiewicz, M. Woińska, K. Woźniak, IUCRJ, 7(6) (2020) 1199-1215, https://doi.org/10.1107/S2052252520013603

[6] M. L. Chodkiewicz, R. Gajda, B. Lavina, S. Tkachev, V. B. Prakapenka, P. Dera, K. Woźniak, IUCRJ, 9(5) (2022), https://doi.org/10.1107/S2052252522006662

[7] M. Woińska, M. L. Chodkiewicz, K. Woźniak, ChemCommun., 57 (2021) 3652-3655, https://doi.org/10.1039/D0CC07661A

[8] S. Pawledzio, M. Malinska, M. Woiǹska, J. Wojciechowski, L. A. Malaspina, F. Kleemiss, S. Grabowsky, K. Wozniak, IUCrJ, 8 (4) (2021) 608-620, https://doi.org/10.1107/S2052252521004541

[9] S. Pawlędzio, M. Malinska, F. Kleemiss, S. Grabowsky, K. Woźniak, IUCRJ, 9(4) (2022) 497-507, https://doi.org/10.1107/S2052252522005309

Biographical Information:

https://crystal.chem.uw.edu.pl/head-of-the-lab/

Upcoming and Previous CDAC Talks:

https://cdac.phys.uic.edu/cdac-webinar-series/

Recorded CDAC Talks:

https://www.youtube.com/channel/UCah_ErVY7qVCRief1WaF7hA?view_as=subscriber