The dependence of the velocity autocorrelation function on the intermolecular potential and on the memory function
1984; American Institute of Physics; Volume: 81; Issue: 11 Linguagem: Inglês
10.1063/1.447459
ISSN1520-9032
Autores Tópico(s)Chemical Thermodynamics and Molecular Structure
ResumoA new molecular dynamics algorithm enables us to calculate the coefficients in the Mori expansion of the velocity autocorrelation function φ(t) accurately. These coefficients are used to analyze the influence of the attractive forces and to find memory functions for φ. The results for a Lennard-Jones system show that the attractive forces contribute to φ with a Gaussian-like term and with the maximum at a time which corresponds to about five mean collision times. The effect on φ of increasing the density can be separated into a short-time effect, caused by a short-time memory, and an effect of the same form and location as the effect from the attractive forces. The short-time memory can be described by a simple Gaussian and with a relaxation time in good agreement with the mean collision time obtained from perturbation theories.
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