On the increase of the melting temperature of water confined in one- dimensional nano-cavities

F Della Pia and AD Zen and V Kapil and FL Thiemann and D Alfe and A Michaelides, JOURNAL OF CHEMICAL PHYSICS, 161, 224706 (2024).

DOI: 10.1063/5.0239452

Water confined in nanoscale cavities plays a crucial role in everyday phenomena in geology and biology, as well as technological applications at the water-energy nexus. However, even understanding the basic properties of nano-confined water is extremely challenging for theory, simulations, and experiments. In particular, determining the melting temperature of quasi-one-dimensional ice polymorphs confined in carbon nanotubes has proven to be an exceptionally difficult task, with previous experimental and classical simulation approaches reporting values ranging from similar to 180 K up to similar to 450 K at ambient pressure. In this work, we use a machine learning potential that delivers first principles accuracy (trained to the density functional theory approximation revPBE0-D3) to study the phase diagram of water for confinement diameters 9.5 < d < 12.5 & Aring;. We find that several distinct ice polymorphs melt in a surprisingly narrow range between similar to 280 and similar to 310 K, with a melting mechanism that depends on the nanotube diameter. These results shed new light on the melting of ice in one-dimension and have implications for the operating conditions of carbon-based filtration and desalination devices.

Return to Publications page