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Time correlations and the second entropy Angus Gray-Weale and Phil Attard

Summary: Time correlations and the second entropy
Angus Gray-Weale and Phil Attard
School of Chemistry F11, University of Sydney, New South Wales 2006, Australia
Received 20 April 2007; accepted 11 June 2007; published online 25 July 2007
The authors study the transport of mass and heat in simulations of a Lennard-Jones fluid and
demonstrate the calculation of transport coefficients, and of both the first and second entropies.
These entropies are calculated from time correlation functions, as are the transport coefficients.
They discuss the role of the second entropy in providing a physical explanation for the link between
dynamic fluctuations and response. They illustrate the physical significance of the various
contributions to the second entropy and how they simplify in the case of relaxation by steady-state
flow. Certain approximations proposed for the calculation of the first entropy, common in the
literature, are shown to break down under certain circumstances, and they give an improved method
of calculation. They pay particular attention to the coupling between variables of opposite time
parity in the transport matrix, and show that in general this cannot be neglected. 2007 American
Institute of Physics. DOI: 10.1063/1.2754271
Macroscopic fluxes of heat or matter due to applied ther-
modynamic or mechanical forces are described by the hydro-
dynamic transport laws. Such laws rely upon the existence of
the linear transport coefficients and upon local thermal equi-


Source: Attard, Phil - School of Chemistry, University of Sydney


Collections: Chemistry