Role of attractive forces in determining the equilibrium structure and dynamics of simple liquids

TL;DR

This study uses Molecular Dynamics simulations to explore how attractive forces influence the structure and dynamics of Lennard-Jones liquids, revealing their significance beyond the first coordination shell and their impact on pressure and diffusion.

Contribution

It demonstrates that attractive forces outside the first coordination shell affect the structure and dynamics of simple liquids, extending understanding beyond condensed phases.

Findings

Attractive forces modify radial distribution functions.

Neglecting attractions leads to overestimated pressure.

Long-range attractions damp particle diffusion.

Abstract

Molecular Dynamics simulations of a Lennard-Jones system with different range of attraction show that the attractive forces modify the radial distribution of the particles. For condensed liquids only, the forces within the the first coordination shell (FCS) are important, but for gases and moderate condensed fluids, even the attractive forces outside the FCS play a role. The changes in the distribution caused by neglecting the attractive forces, lead to a too high pressure. The weak long-range attractions damp the dynamics and the diffusion of the particles in gas-, super critical fluid- and in liquid states. The values of self-diffusion coefficients (SDC) agree qualitatively with a modified Cohen-Turnbull model. The SDC-s along the critical isotherm show no anomaly at the critical point in agreement with experimental data.