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Chodkiewicz ML, Gajda R, Lavina B, Tkachev S, Prakapenka VB, Dera P, Wozniak K. Accurate crystal structure of ice VI from X-ray diffraction with Hirshfeld atom refinement. IUCRJ 2022; 9:573-579. [PMID: 36071798 PMCID: PMC9438488 DOI: 10.1107/s2052252522006662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 06/28/2022] [Indexed: 06/15/2023]
Abstract
Water is an essential chemical compound for living organisms, and twenty of its different crystal solid forms (ices) are known. Still, there are many fundamental problems with these structures such as establishing the correct positions and thermal motions of hydrogen atoms. The list of ice structures is not yet complete as DFT calculations have suggested the existence of additional and - to date - unknown phases. In many ice structures, neither neutron diffraction nor DFT calculations nor X-ray diffraction methods can easily solve the problem of hydrogen atom disorder or accurately determine their anisotropic displacement parameters (ADPs). Here, accurate crystal structures of H2O, D2O and mixed (50%H2O/50%D2O) ice VI obtained by Hirshfeld atom refinement (HAR) of high-pressure single-crystal synchrotron and laboratory X-ray diffraction data are presented. It was possible to obtain O-H/D bond lengths and ADPs for disordered hydrogen atoms which are in good agreement with the corresponding single-crystal neutron diffraction data. These results show that HAR combined with X-ray diffraction can compete with neutron diffraction in detailed studies of polymorphic forms of ice and crystals of other hydrogen-rich compounds. As neutron diffraction is relatively expensive, requires larger crystals which can be difficult to obtain and access to neutron facilities is restricted, cheaper and more accessible X-ray measurements combined with HAR can facilitate the verification of the existing ice polymorphs and the quest for new ones.
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Affiliation(s)
- Michal L. Chodkiewicz
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury, Warszawa 02-089, Poland
| | - Roman Gajda
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury, Warszawa 02-089, Poland
| | - Barbara Lavina
- Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Sergey Tkachev
- Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439, USA
| | - Vitali B. Prakapenka
- Hawai’i Institute of Geophysics and Planetology, Université d’hawaï à mānoa, 1680 East-West Road, Honolulu, HI 96822, USA
| | - Przemyslaw Dera
- Hawai’i Institute of Geophysics and Planetology, Université d’hawaï à mānoa, 1680 East-West Road, Honolulu, HI 96822, USA
| | - Krzysztof Wozniak
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Żwirki i Wigury, Warszawa 02-089, Poland
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