Adapting SAFTγ perturbation theory to sitebased molecular dynamics simulation. II. Confined fluids and vaporliquid interfaces
Abstract
In this work, a new classical density functional theory is developed for groupcontribution equations of state (EOS). Details of implementation are demonstrated for the recentlydeveloped SAFTγ WCA EOS and selective applications are studied for confined fluids and vaporliquid interfaces. The acronym WCA (WeeksChandlerAndersen) refers to the characterization of the reference part of the thirdorder thermodynamic perturbation theory applied in formulating the EOS. SAFTγ refers to the particular form of “statistical associating fluid theory” that is applied to the fusedsphere, heteronuclear, unitedatom molecular models of interest. For the monomer term, the modified fundamental measure theory is extended to WCAspheres. A new chain functional is also introduced for fused and soft heteronuclear chains. The attractive interactions are taken into account by considering the structure of the fluid, thus elevating the theory beyond the mean field approximation. The fluctuations of energy are also included via a nonlocal thirdorder perturbation theory. The theory includes resolution of the density profiles of individual groups such as CH{sub 2} and CH{sub 3} and satisfies stoichiometric constraints for the density profiles. New molecular simulations are conducted to demonstrate the accuracy of each Helmholtz free energy contribution in reproducing the microstructure of inhomogeneous systems at the unitedatom level ofmore »
 Authors:
 Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325 (United States)
 Publication Date:
 OSTI Identifier:
 22308581
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACCURACY; COMPARATIVE EVALUATIONS; DENSITY; DENSITY FUNCTIONAL METHOD; EQUATIONS OF STATE; ETHANE; FREE ENERGY; HEPTANE; INTERFACES; LIQUIDS; MEASURE THEORY; MICROSTRUCTURE; MOLECULAR DYNAMICS METHOD; MOLECULAR MODELS; PERTURBATION THEORY; SIMULATION; SURFACE TENSION; VAPORS
Citation Formats
Ghobadi, Ahmadreza F., and Elliott, J. Richard, Email: elliot1@uakron.edu. Adapting SAFTγ perturbation theory to sitebased molecular dynamics simulation. II. Confined fluids and vaporliquid interfaces. United States: N. p., 2014.
Web. doi:10.1063/1.4886398.
Ghobadi, Ahmadreza F., & Elliott, J. Richard, Email: elliot1@uakron.edu. Adapting SAFTγ perturbation theory to sitebased molecular dynamics simulation. II. Confined fluids and vaporliquid interfaces. United States. doi:10.1063/1.4886398.
Ghobadi, Ahmadreza F., and Elliott, J. Richard, Email: elliot1@uakron.edu. Mon .
"Adapting SAFTγ perturbation theory to sitebased molecular dynamics simulation. II. Confined fluids and vaporliquid interfaces". United States.
doi:10.1063/1.4886398.
@article{osti_22308581,
title = {Adapting SAFTγ perturbation theory to sitebased molecular dynamics simulation. II. Confined fluids and vaporliquid interfaces},
author = {Ghobadi, Ahmadreza F. and Elliott, J. Richard, Email: elliot1@uakron.edu},
abstractNote = {In this work, a new classical density functional theory is developed for groupcontribution equations of state (EOS). Details of implementation are demonstrated for the recentlydeveloped SAFTγ WCA EOS and selective applications are studied for confined fluids and vaporliquid interfaces. The acronym WCA (WeeksChandlerAndersen) refers to the characterization of the reference part of the thirdorder thermodynamic perturbation theory applied in formulating the EOS. SAFTγ refers to the particular form of “statistical associating fluid theory” that is applied to the fusedsphere, heteronuclear, unitedatom molecular models of interest. For the monomer term, the modified fundamental measure theory is extended to WCAspheres. A new chain functional is also introduced for fused and soft heteronuclear chains. The attractive interactions are taken into account by considering the structure of the fluid, thus elevating the theory beyond the mean field approximation. The fluctuations of energy are also included via a nonlocal thirdorder perturbation theory. The theory includes resolution of the density profiles of individual groups such as CH{sub 2} and CH{sub 3} and satisfies stoichiometric constraints for the density profiles. New molecular simulations are conducted to demonstrate the accuracy of each Helmholtz free energy contribution in reproducing the microstructure of inhomogeneous systems at the unitedatom level of coarse graining. At each stage, comparisons are made to assess where the present theory stands relative to the current state of the art for studying inhomogeneous fluids. Overall, it is shown that the characteristic features of real molecular fluids are captured both qualitatively and quantitatively. For example, the average pore density deviates ∼2% from simulation data for attractive pentadecane in a 2nm slit pore. Another example is the surface tension of ethane/heptane mixture, which deviates ∼1% from simulation data while the theory reproduces the excess accumulation of ethane at the interface.},
doi = {10.1063/1.4886398},
journal = {Journal of Chemical Physics},
number = 2,
volume = 141,
place = {United States},
year = {Mon Jul 14 00:00:00 EDT 2014},
month = {Mon Jul 14 00:00:00 EDT 2014}
}

In Paper I [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 139(23), 234104 (2013)], we showed that how a thirdorder Weeks–Chandler–Anderson (WCA) Thermodynamic Perturbation Theory and molecular simulation can be integrated to characterize the repulsive and dispersive contributions to the Helmholtz free energy for realistic molecular conformations. To this end, we focused on nalkanes to develop a theory for fused and soft chains. In Paper II [A. F. Ghobadi and J. R. Elliott, J. Chem. Phys. 141(2), 024708 (2014)], we adapted the classical Density Functional Theory and studied the microstructure of the realistic molecular fluids in confined geometriesmore »

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Extensive molecular dynamics simulations are carried out to study the molecular interactions, liquid states, and liquid/vapor properties of dichloromethane. The study is also extended to the equilibrium properties of the liquid/liquid interface of waterdichloromethane. The intermolecular interactions among water, dichloromethane, and waterdichloromethane are described using our polarizable potential models. The equilibrium properties of liquid dichloromethane, including the radial distribution functions, the intermolecular structural factor, the selfdiffusion coefficient, and the dielectric constant, are evaluated. The dielectric constant is computed using Ewald summation techniques and the computed result compared reasonably well with the available experimental data. Properties such as surface tensions andmore »