Theoretical equations of state for temperature and electromagnetic field dependence of fluid systems, based on the quasi-Gaussian entropy theory
Amadei A, Apol MEF, Brancato G, Di Nola A
JOURNAL OF CHEMICAL PHYSICS
116 (11): 4437-4449 MAR 15 2002

FULL TEXT

Abstract:

The quasi-Gaussian entropy (QGE) theory employs the fact that a free-energy change can be written as the moment-generating function of the appropriate probability distribution function of macroscopic fluctuations of an extensive property. By modeling this distribution, one obtains a model of free energy and resulting thermodynamics as a function of one state variable. In this paper the QGE theory has been extended towards theoretical models or equations of state (EOS's) of the thermodynamics of semiclassical systems as a function of two state variables. Two "monovariate" QGE models are combined in the canonical ensemble: one based on fluctuations of the excess energy (the confined gamma state giving the temperature dependence) and the other based on fluctuations of the reduced electromagnetic moment [various models as derived in the preceding paper [Apol, Amadei, and Di Nola, J. Chem. Phys. 116, 4426 (2002)], giving the external field dependence]. This provides theoretical EOS's for fluid systems as a function of both temperature and electromagnetic field. Special limits of these EOS's are considered: the general weak-field EOS and the limit to a Curie's law behavior. Based on experimental data of water and simulation data using the extended simple point charge (SPC/E) water model at 45.0 and 55.51 mol/dm(3), the specific EOS based on a relatively simple combination of the confined gamma state model with a discrete uniform state field model accurately reproduces the dielectric properties of water at constant density, as the temperature dependence of the weak-field dielectric constant for gases and liquids, and the field dependence of the dielectric constant of liquids. (C) 2002 American Institute of Physics.

KeyWords Plus:

MOLECULAR-DYNAMICS SIMULATIONS, PARTICLE MESH EWALD, THERMODYNAMIC PROPERTIES, NONCANONICAL ENSEMBLES, COMPUTER-SIMULATIONS, FLUCTUATION FORMULAS, DIELECTRIC-CONSTANT, WATER MODELS, DERIVATION, STEAM

Addresses:

Amadei A, Univ Roma Tor Vergata, Dept Chem Sci & Technol, Via Ric Sci 1, I-00133 Rome, Italy
Univ Roma Tor Vergata, Dept Chem Sci & Technol, I-00133 Rome, Italy
Univ Roma La Sapienza, Dept Chem, I-00185 Rome, Italy
Univ Groningen, Dept Biophys Chem, NL-9747 AG Groningen, Netherlands