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Monte Carlo simulations of liquids : polydispersity and the Gibbs ensemble

Monte Carlo simulations of liquids : polydispersity and the Gibbs ensemble
Monte Carlo simulations of liquids : polydispersity and the Gibbs ensemble

Monte Carlo simulations of polydisperse hard sphere fluids have been performed in three different ensembles. In the canonical ensemble we have compared the convergence properties of a conventional Metropolis approach with those of a smart sampling method. The isothermal-isobaric ensemble is used to confirm the accuracy of the polydisperse form of the Camahan-Starling equation for large degrees of polydispersity. Simulations in the grand canonical ensemble formed an independent check on our polydisperse simulation methodology. A simple perturbation theory is developed to support the simulation results. The competing effects of size and energy polydispersity in the Lennard-Jones model fluid have been investigated. We demonstrate the important role played by the correlation between particle size and well-depth in determining the thermodynamic and structural properties of polydisperse liquids.

The Gibbs ensemble simulation method for determining the phase coexistence properties of a model fluid is described in detail, and applied to the calculation of liquid-vapour phase equilibria in the pure Lennard-Jones fluid. System size effects in the Gibbs ensemble are investigated. The Gibbs methodology is extended to study liquid-vapour equilibria in three binary Lennard-Jones mixtures, and membrane equilibria in an ideal mixture. The application of the Gibbs method to molecular fluids is discussed. Calculations are reported for liquid-vapour equilibria in pure quadrupolar fluids, and in a binary quadrupole mixture. The simulation results are compared to the predictions of thermodynamic perturbation theory. The Gibbs ensemble and our polydisperse simulation methodology are combined. We show that size polydispersiy, and correlated size and energy polydispersity, can have a significant effect on the phase coexistence properties of the Lennard-Jones fluid.

University of Southampton
Stapleton, Michael Robert
Stapleton, Michael Robert

Stapleton, Michael Robert (1988) Monte Carlo simulations of liquids : polydispersity and the Gibbs ensemble. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Monte Carlo simulations of polydisperse hard sphere fluids have been performed in three different ensembles. In the canonical ensemble we have compared the convergence properties of a conventional Metropolis approach with those of a smart sampling method. The isothermal-isobaric ensemble is used to confirm the accuracy of the polydisperse form of the Camahan-Starling equation for large degrees of polydispersity. Simulations in the grand canonical ensemble formed an independent check on our polydisperse simulation methodology. A simple perturbation theory is developed to support the simulation results. The competing effects of size and energy polydispersity in the Lennard-Jones model fluid have been investigated. We demonstrate the important role played by the correlation between particle size and well-depth in determining the thermodynamic and structural properties of polydisperse liquids.

The Gibbs ensemble simulation method for determining the phase coexistence properties of a model fluid is described in detail, and applied to the calculation of liquid-vapour phase equilibria in the pure Lennard-Jones fluid. System size effects in the Gibbs ensemble are investigated. The Gibbs methodology is extended to study liquid-vapour equilibria in three binary Lennard-Jones mixtures, and membrane equilibria in an ideal mixture. The application of the Gibbs method to molecular fluids is discussed. Calculations are reported for liquid-vapour equilibria in pure quadrupolar fluids, and in a binary quadrupole mixture. The simulation results are compared to the predictions of thermodynamic perturbation theory. The Gibbs ensemble and our polydisperse simulation methodology are combined. We show that size polydispersiy, and correlated size and energy polydispersity, can have a significant effect on the phase coexistence properties of the Lennard-Jones fluid.

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Published date: 1988

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Local EPrints ID: 460925
URI: http://eprints.soton.ac.uk/id/eprint/460925
PURE UUID: bd98ed85-d649-432c-aa3f-7a9cf89f66da

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Date deposited: 04 Jul 2022 18:32
Last modified: 04 Jul 2022 18:32

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Author: Michael Robert Stapleton

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