Molecular-level Calculation Scheme for Pressure in Inhomogeneous Systems of Flat and Spherical Layers

Expressions for the microscopic pressure tensor, suitable for use in molecular dynamics (MD) and Monte Carlo simulations, are presented. The expressions apply to heterogeneous systems consisting of particles interacting with pair-wise additive potentials. The normal and transverse components of the pressure tensor as defined by Irving and Kirkwood [Irving, A.J.H. and Kirkwood, J.G. J. Chem. Phys. , 18 (1950) 817] were used to derive explicit equations for the coarse-grained pressure in planar and spherical symmetries. Molecular dynamics simulation results at v /near planar and spherical surfaces confirmed that mechanical balance is attained at equilibrium. Furthermore, it was found that the computed coarse-grained pressure in a local volume was more precise than the pressure on a surface for a given simulation length.