title: Two Dimensional Ice from First Principles: Structures and Phase Transitions.
abstract: Despite relevance to disparate areas such as cloud microphysics and tribology, major gaps in the understanding of the structures and phase transitions of low-dimensional water ice remain. Here, we report a first principles study of confined 2D ice as a function of pressure. We find that at ambient pressure hexagonal and pentagonal monolayer structures are the two lowest enthalpy phases identified. Upon mild compression, the pentagonal structure becomes the most stable and persists up to ∼2  GPa, at which point the square and rhombic phases are stable. The square phase agrees with recent experimental observations of square ice confined within graphene sheets. This work provides a fresh perspective on 2D confined ice, highlighting the sensitivity of the structures observed to both the confining pressure and the width.
authors.affiliation: London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, United Kingdom.|Thomas Young Centre, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: Ji
authors.initials: J
authors.lastname: Chen
authors.affiliation: Thomas Young Centre, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.|Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.|Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
authors.forename: Georg
authors.initials: G
authors.lastname: Schusteritsch
authors.affiliation: Thomas Young Centre, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.|Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.|Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Pickard
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
authors.forename: Christoph G
authors.initials: CG
authors.lastname: Salzmann
authors.affiliation: London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, United Kingdom.|Thomas Young Centre, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.|Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Angelos
authors.initials: A
authors.lastname: Michaelides