Accurate crystal structure of ice VI from X-ray diffraction with Hirshfeld atom refinement

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.

Current developments and trends in quantum crystallography

“…Furthermore, one should not overlook the fact that, at approximately the same time, the DISCaMB (densities in structural chemistry and molecular biology) library (Chodkiewicz et al, 2018) was also linked to Olex2 and the Warsaw branch of HAR was introduced (Chodkiewicz et al, 2020). This was later applied to several problems (some of them discussed in the following paragraphs), such as determining the positions of hydrogen atoms bonded to heavy metals (Woin ´ska et al, 2021(Woin ´ska et al, , 2023, fragmentation and transferability (Chodkiewicz, Pawle ˛dzio et al, 2022;Chodkiewicz et al, 2024), and refinement of ice (Chodkiewicz, Gajda et al, 2022) and metal-organic framework (Xu et al, 2023) structures.…”

“…HAR was also successfully used (with and without the inclusion of relativistic effects) to accurately and precisely determine the positions of hydrogen atoms bonded to metal atoms in transition-metal-bound hydride complexes (Woin ´ska et al, 2021(Woin ´ska et al, , 2023. Finally, in the framework of HAR applications, it is worth citing the efforts by Woz ´niak and collaborators to unravel the different structures of ice (Chodkiewicz, Gajda et al, 2022).…”

Elastic and piezoelectric properties of β-glycine – a quantum crystallography view on intermolecular interactions and a high-pressure phase transition

“…Modeling of crystal structures under pressure by DFT methods has been performed for many compounds and functional materials: organic aromatic compounds such as syn-1,6:8,13-biscarbonyl[14]annulene (Casati et al, 2016(Casati et al, , 2017; perovskites (Tariq et al, 2015;Dar et al, 2017;Coduri et al, 2019;Ciupa-Litwa et al, 2020), kaolinites (Richard & Rendtorff, 2022;Richard & Rendtorff, 2022), carbonates (Zhuravlev & Atuchin, 2021;Zhuravlev & Korabel'nikov, 2022) and other inorganic compounds (Faridi et al, 2018;Nazir et al, 2018;Yaseen et al, 2021); grossular (Gajda et al, 2020), ice (Chodkiewicz et al, 2022), zeolites (Stachowicz et al, 2023) and also molecular crystals (Schatschneider et al, 2013;Liu et al, 2014;Moellmann & Grimme, 2014;Matveychuk et al, 2021). Such studies make it possible to predict mechanical, thermodynamic and optoelectronic properties, as well as phase transitions of various types.…”

Evolution of structure and spectroscopic properties of a new 1,3-diacetylpyrene polymorph with temperature and pressure

“…However, since the groundbreaking analysis of aromaticity at high pressure conducted by Casati et al (2016Casati et al ( , 2017, there have been few attempts at application of HAR or quantum crystallographic approaches in general in high-pressure structural analysis. These involved mostly inorganic highsymmetry systems, where challenges inherent to high-pressure structural analysis, such as moderate scattering power, imperfect absorption correction or poor data coverage, have been carefully circumnavigated (Gajda et al, 2020;Gun ´ka et al, 2021;Stachowicz et al, 2023;Chodkiewicz et al, 2022). Unsurprisingly, structure-property studies of organic materials under increased pressure rely predominantly on geometries obtained from theoretically predicted structures, sometimes without the ability to verify the adequacy of the theoretical model due to a lack of reliable high-pressure experimental geometry (Montisci et al, 2023).…”