title: Phase diagram of water in carbon nanotubes.
abstract: A phase diagram of water in single-walled carbon nanotubes at atmospheric pressure is proposed, which summarizes ice structures and their melting points as a function of the tube diameter up to 1.7 nm. The investigation is based on extensive molecular dynamics simulations over numerous thermodynamic states on the temperature-diameter plane. Spontaneous freezing of water in the simulations and the analysis of ice structures at 0 K suggest that there exist at least nine ice phases in the cylindrical space, including those reported by x-ray diffraction studies and those unreported by simulation or experiment. Each ice has a structure that maximizes the number of hydrogen bonds under the cylindrical confinement. The results show that the melting curve has many local maxima, each corresponding to the highest melting point for each ice form. The global maximum in the melting curve is located at approximately 11 A, where water freezes in a square ice nanotube.
authors.affiliation: Department of Chemistry, Faculty of Science, Okayama University, Okayama 700-8530, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Takaiwa
authors.forename: Itaru
authors.initials: I
authors.lastname: Hatano
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Koga
authors.forename: Hideki
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D002621:Chemistry / Q000379:methods*; D003198:Computer Simulation; D019277:Entropy; D005615:Freezing; D006860:Hydrogen Bonding; D007053:Ice; D008968:Molecular Conformation; D036103:Nanotechnology / Q000379:methods; D037742:Nanotubes, Carbon / Q000737:chemistry*; D011312:Pressure; D013696:Temperature; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D007053:Ice; D037742:Nanotubes, Carbon; D014867:Water