Influence of the Periodic Boundary Conditions on the Fluid Structure and on the Thermodynamic Properties Computed from the Molecular Simulations
Résumé
The components of pair distribution function in different directions with respect to the
coordinate system defined by the simulation box are determined for Lennard-Jones fluid
simulated using the Monte Carlo technique in cubic boxes of various size. The approach of
Pratt and Haan is employed to analyze the distortion of isotropic fluid structure due to
the periodic boundary conditions and qualitative agreement is found between the
theoretical and simulated course of particular angular components of distribution
function. The relation between the anisotropy of correlation functions and the system size
dependency of residual energy and compressibility factor is analyzed. The finite size
effects become significantly pronounced in systems with size lower than 5 particle
diameters, especially if the length of the box-edge is equal to a non-integer multiple of
molecular diameter. With increasing temperature the implicit finite size effects on fluid
structure as well as on the thermodynamic properties become less important. The primary
cause of the structure deformation lies in the short-range interparticle correlations and
the long-range interactions are not important; therefore, the implicit finite size effects
influence all kinds of atomistic simulations, including those using the interactions of
finite range and in the molecular dynamics simulations. However, at present the simulated
systems are usually of sufficiently large size and ignoring the implicit finite size does
not lead to serious problems, except for the determination of surface properties using the
inhomogeneous simulations which are more sensitive to the lateral dimension of simulation
box.
Domaines
Physique [physics]
Origine : Publication financée par une institution