Fluctuations on the approach to equilibrium: Molecular dynamics study of rotational correlations for vibrating molecules

Abstract

The results of a molecular dynamics study of rotational correlations for vibrating molecules is presented within the context of the Gordon local-equilibrium conjecture: Nonequilibrium fluctuations approach equilibrium faster than the average correlation function approaches equilibrium. For the Diestler–Riehl model for CH3I in three dimensions at two frequencies 83.6 and 526 cm−1 and at a temperature of 300 °K the Gordon conjecture was verified. In the low frequency case a harmonic oscillator potential was used for each molecule but for the high frequency case an anharmonic potential was used. The decay times for the rotational correlation functions for the low and high frequency models, respectively, were τ=1.2 psec and τ=1.3 psec. For the root mean square fluctuations about the average rotational correlations the decay times were τ=0.57 psec and τ=0.55 psec for the low and high frequency models, respectively.