title: Commensurability Effects in Viscosity of Nanoconfined Water.
abstract: The rate of water flow through hydrophobic nanocapillaries is greatly enhanced as compared to that expected from macroscopic hydrodynamics. This phenomenon is usually described in terms of a relatively large slip length, which is in turn defined by such microscopic properties as the friction between water and capillary surfaces and the viscosity of water. We show that the viscosity of water and, therefore, its flow rate are profoundly affected by the layered structure of confined water if the capillary size becomes less than 2 nm. To this end, we study the structure and dynamics of water confined between two parallel graphene layers using equilibrium molecular dynamics simulations. We find that the shear viscosity is not only greatly enhanced for subnanometer capillaries, but also exhibits large oscillations that originate from commensurability between the capillary size and the size of water molecules. Such oscillating behavior of viscosity and, consequently, the slip length should be taken into account in designing and studying graphene-based and similar membranes for desalination and filtration.
authors.affiliation: Department of Physics, Shahid Rajaee Teacher Training University , Lavizan, 16785-136 Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Neek-Amal
authors.affiliation: Departement Fysica, Universiteit Antwerpen , Groenenborgerlaan 171, B-2020 Antwerpen, Belgium.
authors.forename: Francois M
authors.initials: FM
authors.lastname: Peeters
authors.affiliation: School of Physics and Astronomy, University of Manchester , Manchester M13 9PL, United Kingdom.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Grigorieva
authors.affiliation: School of Physics and Astronomy, University of Manchester , Manchester M13 9PL, United Kingdom.
authors.forename: Andre K
authors.initials: AK
authors.lastname: Geim
keywords: graphene channel; nanoconfined water; viscosity