Oscillations in Dynamic Correlations of Binary Liquids

Document Type

Article

Publication Date

9-15-1997

Department

Computing

School

Computing Sciences and Computer Engineering

Abstract

Molecular dynamics simulations are performed for a binary liquid mixture (α + β) to measure, among others, the collective velocity auto-correlation function Zm(t) and the time correlation function of the concentration fluctuations Fm(t). Both α-α and β-β pairs of molecules interact through the same Lenard-Jones potential, but α-β pairs interact only through the repulsive part of the potential. From the results for the relaxation time of Fm(t), we estimate the mutual diffusion coefficients. All measurements probing the individual molecular motions indicate that the molecules execute randomly diffusing motions both at T > TC and T < TC. The measurements probing their collective motions indicate otherwise. At T > TC, the results are as expected from those of the individual motions. At T < TC, the results indicate cooperative behavior which is not evident in the individual motions. Most importantly, we observe an oscillatory mode of collective motions which is analogous to the optical phonons in two-component crystals.

Publication Title

Physica A: Statistical Mechanics and its Applications

Volume

243

Issue

41337

First Page

229

Last Page

242

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