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Ice Nanoribbons Confined in Uniaxially Distorted Carbon Nanotubes

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journal contribution
posted on 27.07.2018, 00:00 by Haruka Kyakuno, Hiroto Ogura, Kazuyuki Matsuda, Yutaka Maniwa
Water confined inside nanopores exhibits unusual static and dynamic properties that depend on the pore size, pore topology, and hydrophobicity and roughness of the pore walls. The properties also depend on the geometrical shape of the pore cross sections. Here, we investigated water inside distorted single-wall carbon nanotubes (SWCNTs) by means of classical molecular dynamics calculations, over a temperature range of 100–350 K. SWCNTs, which provide ideal one-dimensional cylindrical pores with atomically smooth nonpolar walls, were uniaxially compressed in a direction perpendicular to the SWCNT axes with a deformation ratio γ up to 60%, where γ represents the ratio of deformation amount to the initial SWCNT diameter D. With increasing γ in an SWCNT with D = 1.24 nm, a hexagonal ice nanotube was converted to the liquid state with high water mobility down to 200 K and then to a new form of ice, ice nanoribbon, consisting of four ferroelectric water chains. In an SWCNT with D = 1.51 nm, on the other hand, the water was converted to an ice nanoribbon with five ferroelectric water chains from the liquid state. It was demonstrated that the application of uniaxial pressure is a useful technique to control water properties, such as dielectricity, mobilities, and structures.