High pressure partially ionic phase of water ice.
basic_science · Level V
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- Record sourced from PubMed, PMID 22127059.
- Also identified by DOI 10.1038/ncomms1566.
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Abstract
Water ice dissociates into a superionic solid at high temperature (>2,000 K) and pressure, where oxygen forms the lattice, but hydrogen diffuses completely. At low temperature, however, the dissociation into an ionic ice of hydronium (H(3)O)(+) hydroxide (OH)(-) is not expected because of the extremely high energy cost (~1.5 eV) of proton transfer between H(2)O molecules. Here we show the pressure-induced formation of a partially ionic phase (monoclinic P2(1) structure) consisting of coupled alternate layers of (OH)(δ-) and (H(3)O)(δ+) (δ=0.62) in water ice predicted by particle-swarm optimization structural search at zero temperature and pressures of >14 Mbar. The occurrence of this ionic phase follows the break-up of the typical O-H covalently bonded tetrahedrons in the hydrogen symmetric atomic phases and is originated from the volume reduction favourable for a denser structure packing.
Medical subject headings
- Ice
- Water