Simulation Studies of a Lennard-Jones Liquid in Micropores

Abstract

In this paper grand canonical ensemble Monte Carlo and molecular dynamics simulation techniques are used to establish the degree to which the equilibrium and transport properties of fluids in micropores are influenced both by confinement in the narrow pore space and by the lattice structure of the pore wall. Partition coefficients, solvation forces, and diffusion coefficients for a Lennard-Jones liquid confined within two model cylindrical pores are determined over a range of effective micropore sizes. In one model the cylindrical pore wall is described by a structureless, continuum interaction potential similar to that which is frequently employed in theoretical studies of adsorption. In the second model a single embedded layer of lattice atoms is placed at the solid/fluid interface.

The results obtained are compared with the prediction of a bulk fluid approximation and the Fischer-Methfessel approximation to the Yvon-Born-Green equation and the recently developed kinetic theory of Davis for micropore fluids. These theories are shown to agree very favorably with the simulation results for the structureless model although quantitatively less so for pores with structured walls.

Key Words:

• Micropores
• Lennard-Jones fluid
• density profiles
• solvation forces
• diffusion