Published August 16, 2020 | Version v1
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Insights into water permeation through hBN nanocapillaries by ab initio machine learning molecular dynamics simulations

  • 1. Data Science Hub, Flemish Institute for Technological Research (VITO), 2400 Mol, Belgium
  • 2. Departement Fysica, Universiteit Antwerpen, 2020 Antwerpen, Belgium
  • 3. Institut für Physikalische Chemie, Theoretische Chemie, Universität Göttingen, 37077 Göttingen, Germany

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Description

Water permeation between stacked layers of hBN sheets forming 2D nanochannels is investigated using large-scale ab initio-quality molecular dynamics simulations. A high-dimensional neural network potential trained on density functional theory calculations is employed. We simulate water in van der Waals nanocapillaries and study the impact of nanometric confinement on the structure and dynamics of water using both equilibrium and nonequilibrium methods. At an interlayer distance of 10.2 Å confinement induces a first-order phase transition resulting in a well-defined AA-stacked bilayer of hexagonal ice. In contrast, for h < 9 Å, the 2D water monolayer consists of a mixture of different locally ordered patterns of squares, pentagons, and hexagons. We found a significant change in the transport properties of confined water, particularly for monolayer water where the water−solid friction coefficient decreases to half and the diffusion coefficient increases by a factor of 4 as compared to bulk water. Accordingly, the slip-velocity is found to increase under confinement and we found that the overall permeation is dominated by monolayer water adjacent to the hBN membranes at extreme confinements. We conclude that monolayer water in addition to bilayer ice has a major contribution to water transport through 2D nanochannels.

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References

Journal reference (Paper in which the method is described)
H. Ghorbanfekr, J. Behler, F. M. Peeters, J. Phys. Chem. Lett. (2020), doi: 10.1021/acs.jpclett.0c01739

Journal reference (Paper in which the method is described)
H. Ghorbanfekr, J. Behler, F. M. Peeters, J. Phys. Chem. Lett. (2020)