On the application of virtual Gibbs ensembles to the direct simulation of fluid–fluid and solid–fluid phase coexistence

Shetty, Ritesh; Escobedo, Fernando A.

doi:10.1063/1.1467899

Cited by 9 publications

(4 citation statements)

References 25 publications

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“…The use of molecular simulation techniques is becoming a routine way to predict equilibrium thermodynamic properties of fluids and fluid mixtures. Indeed, in recent years, important improvements have been made in simulation methodology and several efficient algorithms are available to obtain an entire liquid-vapor coexistence curve through different methods ͑Gibbs Ensemble Monte Carlo, [1][2][3] Virtual Gibbs Ensemble, 4 Histogram Reweighting, 5 Hamiltonian Scaling, 6,7 Gibbs-Duhem Integration, 8,9 ...͒. Nevertheless, despite those real progresses, property prediction is not yet a standard practice in industrial applications.…”

Section: Introductionmentioning

confidence: 99%

New optimization method for intermolecular potentials: Optimization of a new anisotropic united atoms potential for olefins: Prediction of equilibrium properties

Bourasseau

Haboudou

Boutin

et al. 2003

The Journal of Chemical Physics

148

192

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In this study, we propose a new global procedure to perform optimization of semiempirical intermolecular potential parameters on the basis of a large reference database. To obtain transferable parameters, we used the original method proposed by Ungerer ͓Ungerer et al., J. Chem. Phys. 112, 5499 ͑2000͔͒, based on the minimization of a dimensionless error criterion. This method allows the simultaneous optimization of several parameters from a large set of reference data. However, the computational cost of such a method limits its application, because it implies the calculation of an important number of partial derivatives, calculated by finite differences between the results of several different simulations. In this work, we propose a new method to evaluate partial derivatives, in order to reduce the computing time and to obtain more consistent derivatives. This method is based on the analysis of statistical fluctuations during a single simulation. To predict equilibrium properties of olefins, we optimize the Lennard-Jones potential parameters of the unsaturated hydrocarbon groups using the anisotropic united atoms description. The resulting parameters are consistent with those previously determined for linear and branched alkanes. Test simulations have been performed at temperatures ranging from 150 to 510 K for several ␣-olefins ͑ethylene, propene, 1-butene, 1-pentene, 1-hexene, 1-octene͒, several ␤-olefins ͑trans-2-butene, cis-2-butene, trans-2-pentene͒, isobutene, and butadiene. Equilibrium properties are well predicted, and critical properties can be evaluated with a good accuracy, despite the fact that most of the results constitute pure predictions. It is concluded that the AUA potential, due to a relevant physical meaning, can be transferred to a large range of olefins with good success.

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Section: Introductionmentioning

confidence: 99%

New optimization method for intermolecular potentials: Optimization of a new anisotropic united atoms potential for olefins: Prediction of equilibrium properties

Bourasseau

Haboudou

Boutin

et al. 2003

The Journal of Chemical Physics

148

192

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“…Other variants of the VGE as described in Ref. 17 were explored, but the above variant gave proper density convergence. Periodic boundary conditions in the x and y directions were implemented for the surfactant monolayer.…”

Section: Computational Modelsmentioning

confidence: 99%

Phase equilibria in model surfactants forming Langmuir monolayers

Ramírez

Santana

Cruz

et al. 2007

The Journal of Chemical Physics

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The study of Langmuir monolayers has generated the attention of researchers because of their unique properties and their not well understood phase equilibrium. These monolayers exhibit interesting phase diagrams where the unusual liquid-liquid equilibrium can be observed for a single component monolayer. Monte Carlo computer simulations in the virtual Gibbs ensemble were used to obtain the phase diagram of Langmuir monolayers. The liquid-vapor and liquid-liquid phase equilibria were considered by constructing the Cailletet-Mathias phase diagrams. By using the Ising model and the rectilinear approximations the identification of the critical properties for both equilibria was determined. These critical parameters were calculated as a function of the strength of the interaction between the surfactant molecules and the aqueous subphase. As a result, we have identified the coexistence between a liquid expanded state (LES)-vapor and the liquid condensed state-LES, in agreement with experimental and theoretical evidence in the literature. We obtained a clear separation of phases and a strong dependence on the strength of the solvent used. Namely, as the interaction between the solvent and the head of the surfactant increases, the critical properties also increase. Equilibrium states were characterized by computing thermodynamic quantities as a function of temperature and solvent strength.

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“…Other available techniques include grand canonical Monte Carlo simulations, the Kirkwood coupling method, Gibbs−Duhem integration, 48-50 the virtual Gibbs ensemble, and integral equation methods. , Of these, the simplest and by far least demanding from a computational point of view are the methods based on Widom insertion. We have performed the molecular modeling of our test system using the Widom method (i.e., via the use of eq 12), as is commonly implemented, and have compared the results with the simulation of the same system via direct MD methods.…”

Section: Simulation Of Scf−solid Equilibriamentioning

confidence: 99%

On the Calculation of Supercritical Fluid−Solid Equilibria by Molecular Simulation

and

Müller

2003

J. Phys. Chem. B

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Methods and intermolecular potentials apt for the molecular simulation of solubilities of solids in supercritical fluids are briefly reviewed. As an illustrative example, the solubilities of naphthalene in supercritical carbon dioxide at 328.15 K are studied using an isotropic multipolar potential model. Upon using the Widom insertion method, a quantitative prediction of the experimental data is obtained. A further look at the calculations shows that the customary implementation of the method is tainted by the use of experimental information about the vapor pressure and density of the solid. If the actual properties (obtained via simulation) of the model solid are used, the equilibrium is, in this example, poorly described. Full-scale molecular dynamic simulations, which include both the solid and fluid phases, confirm the results. It is shown how an accurate description and modeling of the solute solid-phase properties is a prerequisite for the determination of the solubilities of solids in supercritical fluids.

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On the application of virtual Gibbs ensembles to the direct simulation of fluid–fluid and solid–fluid phase coexistence

Cited by 9 publications

References 25 publications

New optimization method for intermolecular potentials: Optimization of a new anisotropic united atoms potential for olefins: Prediction of equilibrium properties

New optimization method for intermolecular potentials: Optimization of a new anisotropic united atoms potential for olefins: Prediction of equilibrium properties

Phase equilibria in model surfactants forming Langmuir monolayers

On the Calculation of Supercritical Fluid−Solid Equilibria by Molecular Simulation

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