Molecular dynamics studies of Lennard-Jones liquid mixtures. I. Role of attractive term in the behavior of one different particle

Abstract

Molecular dynamics calculations have been made for three kinds of fluid systems each containing 108 Lennard‐Jones particles. In the first reference system, the values of the potential parameters for all the particles were assumed to be those of argon. In order to examine the effect of the attractive term, each particle (referred to as the solute) in the other two systems was assumed to have different values for the energy parameter of the potential, ε₁₂. The ε₁₂ value assigned was either twice or half that of the ε₁₁ value for all the other particles (referred to as the solvent), while the σ value was common to all the particles. Both equilibrium and transport properties, as well as cooperative and relaxation phenomena, were calculated and discussed. Among others, the following important results were obtained. The position and height of the first peak of the solute–solvent radial distribution function change appreciably and systematically with ε₁₂. The self‐diffusion coefficient of the solute becomes larger as ε₁₂ decreases, and in contrast to the somewhat gaslike motion of the 0.5ε solute, the oscillatory nature of the motion of the 2.0ε solute was clearly seen from the velocity autocorrelation function for each solute. The time dependence of the pair correlation functions and the correlation between solute and neighboring solvents were also investigated. The correlations of the motion of neighboring solvents with that of the central solute, especially of 2.0ε solute, were found to be unexpectedly large for the first neighbors as compared with those for the particles outside them.