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Ice in a tube: new phases of water at the nanoscale and a solid–liquid critical point

Erik E. Santiso
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA

Commentary on

K. Koga, G.T. Gao, H. Tanaka and X.C. Zeng, “Formation of ordered ice nanotubes inside carbon nanotubes”, Nature, 412:802–805 (2001), https://doi.org/10.1038/35090532

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Statement of Significance

The 2001 paper by Koga, Gao, Tanaka, and Zeng is a landmark in the molecular simulation of confined fluids. Using molecular dynamics simulations, they revealed that water encapsulated inside single-walled carbon nanotubes of sub-nanometer diameter can form entirely new phases of ice - square, pentagonal, hexagonal, and heptagonal nanotube structures - with no counterpart in bulk water. More remarkably, the paper presented evidence for a solid-liquid critical point in a quasi-one-dimensional system, a phenomenon thermodynamically forbidden in the bulk. Published in Nature at a time when carbon nanotubes were attracting intense interest as nanoscale capillaries and templates, this paper launched a new field of research. It has accumulated over a thousand citations and continues to motivate work on nanofluidics, nanotube-confined phase behavior, pressure in nanoscale systems, and the use of molecular simulation to uncover fundamentally new physics inaccessible to experiment alone.

How to cite

Cite the commentary as:

Erik E. Santiso, "Ice in a tube: new phases of water at the nanoscale and a solid–liquid critical point",
KIM REVIEW, Volume 4, Article 03, 2026. DOI: 10.25950/6e3f95ad