Recent experimental results suggest that stacked layers of graphene oxide exhibit
strong selective permeability to water. To construe this observation the transport
mechanism of water permeating through a membrane consisting of layered graphene
sheets is investigated via non-equilibrium and equilibrium molecular dynamics simulations.
The effect of sheet geometry is studied by changing the offset between the
entrance and exit slits of the membrane. The simulation results reveal that the permeability
is not solely dominated by entrance effects; the path traversed by water
molecules has a considerable impact on the permeability. We show that contrary to
speculation in the literature, water molecules do not pass through the membrane as a
hydrogen-bonded chain; instead, they form well-mixed fluid regions confined between
the graphene sheets. The results of the present work are used to provide guidelines
for the development of graphene and graphene oxide membranes for desalination and
solvent separation.