Implicit Finite-Size Effects in Computer Simulations

TL;DR

This paper investigates how periodic boundary conditions affect pair correlations in dense fluids through molecular dynamics simulations and compares the results with theoretical predictions, highlighting finite-size effects and corrections.

Contribution

It provides a detailed comparison of simulation data with theory for finite-size effects on pair correlations in dense fluids near the triple point.

Findings

Significant angular variation in pair correlations for small systems.

Theoretical predictions qualitatively and quantitatively match simulation data.

Finite-size corrections are comparable to statistical errors for typical simulation lengths.

Abstract

The influence of periodic boundary conditions (implicit finite-size effects) on the anisotropy of pair correlations in computer simulations is studied for a dense classical fluid of pair-wise interacting krypton atoms near the triple point. Molecular dynamics simulation data for the pair distribution function of N-particle systems, as a function of radial distance, polar angle, and azimuthal angle are compared directly with corresponding theoretical predictions [L. R. Pratt and S. W. Haan, J. Chem. Phys. 74, 1864 (1981)]. For relatively small systems of N=60, 80, and 108 atoms, significant angular variation is observed, which is qualitatively, and in several cases quantitatively, well predicted by theory. Finite-size corrections to the spherically-averaged radial distribution function, however, are found to be comparable to random statistical errors for runs of 10^5 time steps.