Evidence of low-density and high-density liquid phases and isochore end point for water confined to carbon nanotube

Kentaro Nomura, Toshihiro Kaneko, Jaeil Bai, Joseph S. Francisco, Kenji Yasuoka, Xiao Cheng Zeng

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

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 lowand 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.

Original languageEnglish (US)
Pages (from-to)4066-4071
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number16
DOIs
StatePublished - Apr 18 2017

Keywords

  • Confined water
  • Free energy surface
  • High-density liquid
  • Low-density liquid
  • Molecular dynamics simulation

ASJC Scopus subject areas

  • General

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