Ordinary water ice forms under ambient conditions and has two polytypes, hexagonal ice (Ih) and cubic ice (Ic). From a careful comparison of proton ordering arrangements in Ih and Ic using periodic density functional theory (DFT) and diffusion Monte Carlo (DMC) approaches, we find that the most stable arrangement of water molecules in cubic ice is isoenergetic with that of the proton ordered form of hexagonal ice (known as ice XI). We denote this potential new polytype of ice XI as XIc and discuss a possible route for preparing ice XIc.
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http://dx.doi.org/10.1039/c1cp22506e | DOI Listing |
PeerJ
January 2025
Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico.
The average annual water availability worldwide is approximately 1,386 trillion cubic hectometers (hm), of which 97.5% is saltwater and only 2.5% is freshwater.
View Article and Find Full Text PDFJ Phys Chem Lett
January 2025
DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India.
Clathrate hydrates (CHs) are believed to exist in cold regions of space, such as comets and icy moons. While spectroscopic studies have explored their formation under similar laboratory conditions, direct structural characterization using diffraction techniques has remained elusive. We present the first electron diffraction study of tetrahydrofuran (THF) and 1,3-dioxolane (DIOX) CHs in the form of nanometer-thin ice films under an ultrahigh vacuum at cryogenic temperatures.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00187 Roma, Italy.
Hydrogen hydrates exhibit a rich phase diagram influenced by both pressure and temperature, with the so-called C_{2} phase emerging prominently above 2.5 GPa. In this phase, hydrogen molecules are densely packed within a cubic icelike lattice and the interaction with the surrounding water molecules profoundly affects their quantum rotational dynamics.
View Article and Find Full Text PDFPhys Chem Chem Phys
November 2024
School of Physics, East China University of Science and Technology, Shanghai, 200237, China.
Crystal materials can exhibit novel properties under high pressure, which are completely different from properties under ambient conditions. Water ice has an exceptionally rich phase diagram with at least 20 known crystalline ice phases from experiments, where the high-pressure ice X and ice XVIII behave as an ionic state and a superionic state, respectively. Thus, the ice structures stabilized under high pressure are very likely to possess other novel properties.
View Article and Find Full Text PDFACS Nano
November 2024
Department of Chemistry, Zhejiang University, Hangzhou 310028, P. R. China.
Multitwinned nanocrystals are commonly found in substances that preferentially adopt tetrahedral local arrangements, but not yet in water crystals. Ice nanocrystals are pivotal in cloud microphysics, and their surfaces become increasingly prominent in determining structure as crystal size decreases. Nevertheless, discussions on nanocrystal structures have predominantly centered on ice polymorphs observed in bulk: hexagonal (Ih), cubic (Ic), and stacking-disordered (Isd) ices.
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