title: Evidence of low-density and high-density liquid phases and isochore end point for water confined to carbon nanotube.
abstract: Possible transition between two phases of supercooled liquid water, namely the low- and high-density liquid water, has been only predicted to occur below 230 K from molecular dynamics (MD) simulation. However, such a phase transition cannot be detected in the laboratory because of the so-called "no-man's land" under deeply supercooled condition, where only crystalline ices have been observed. Here, we show MD simulation evidence that, inside an isolated carbon nanotube (CNT) with a diameter of 1.25 nm, both low- and high-density liquid water states can be detected near ambient temperature and above ambient pressure. In the temperature-pressure phase diagram, the low- and high-density liquid water phases are separated by the hexagonal ice nanotube (hINT) phase, and the melting line terminates at the isochore end point near 292 K because of the retracting melting line from 292 to 278 K. Beyond the isochore end point (292 K), low- and high-density liquid becomes indistinguishable. When the pressure is increased from 10 to 600 MPa along the 280-K isotherm, we observe that water inside the 1.25-nm-diameter CNT can undergo low-density liquid to hINT to high-density liquid reentrant first-order transitions.
authors.affiliation: Department of Mechanical Engineering, Keio University, Yokohama 223-8522, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Nomura
authors.affiliation: Department of Mechanical Engineering, Tokyo University of Science, Noda 278-8510, Japan.|Research Institute for Science and Technology, Tokyo University of Science, Noda 278-8510, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kaneko
authors.affiliation: Department of Chemistry, University of Nebraska, Lincoln, NE 68588.
authors.forename: Jaeil
authors.initials: J
authors.lastname: Bai
authors.affiliation: Department of Chemistry, University of Nebraska, Lincoln, NE 68588; jfrancisco3@unl.edu yasuoka@mech.keio.ac.jp xzeng1@unl.edu.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Francisco
authors.affiliation: Department of Mechanical Engineering, Keio University, Yokohama 223-8522, Japan; jfrancisco3@unl.edu yasuoka@mech.keio.ac.jp xzeng1@unl.edu.
authors.forename: Kenji
authors.initials: K
authors.lastname: Yasuoka
authors.affiliation: Department of Chemistry, University of Nebraska, Lincoln, NE 68588; jfrancisco3@unl.edu yasuoka@mech.keio.ac.jp xzeng1@unl.edu.|Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
authors.forename: Xiao Cheng
authors.initials: XC
authors.lastname: Zeng
mesh_terms: D032085:Isochores; D056004:Molecular Dynamics Simulation; D037742:Nanotubes, Carbon / Q000737:chemistry*; D044367:Phase Transition; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D032085:Isochores; D037742:Nanotubes, Carbon; D014867:Water
keywords: confined water; free energy surface; high-density liquid; low-density liquid; molecular dynamics simulation