Transport properties of liquid argon in krypton nanochannels: Anisotropy and non-homogeneity introduced by the solid walls

In this work we calculate the transport properties of liquid argon flowing through a nanochannel formed by krypton walls. Non-equilibrium molecular dynamics (NEMD) simulations are performed assuming flow conditions corresponding to the macroscopic equivalent of planar Poiseuille flow. We examine the effect of channel width and system temperature on diffusion coefficient, shear viscosity and thermal conductivity. The results show clearly the existence of a critical width, in the range 7-18σ, below which the behavior of transport properties is affected in comparison to bulk properties. In fact for small width values, diffusion coefficient is highly anisotropic, the component normal to the wall being the smaller one. For the same width range, diffusivities along all directions are higher in the central layers than those close to the walls. Similarly, shear viscosity increases for small channel width values while thermal conductivity decreases. All properties approach bulk values as the channel width increases. The layers close to the walls always present distinctly different behavior due to the interaction with the wall atoms. The observed behavior is of particular importance in the design of nanofluidic devices.