Prediction of internal structure and properties in fluid model interfaces of binary and ternary liquid mixtures

Kahl, Heike; Mecke, M.; Winkelmann, Jochen

doi:10.1016/j.fluid.2004.09.032

Cited by 10 publications

(6 citation statements)

References 63 publications

(91 reference statements)

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“…This contribution is treated within a Local Density Approximation (LDA) 1,39 , which implies that the hard-sphere contribution to the free energy of the inhomogeneous system is approximated by that of an equivalent homogeneous system of hard spheres evaluated at the local density ρ(r). There are many different DFT versions in the literature that predict the interfacial behaviour of pure and liquid mixtures 70,71,102 , and other more sophisticated that include Non-Local Density Approximations (NLDA) [66][67][68]74,101,[103][104][105] or even take into account explicitly the fluctuations of the system close to the critical point 75 . The use of a LDA is fully justified in the case of planar vapour-liquid interfaces, in which only smooth variations of the density profile exist 1 .…”

Section: Model and Theorymentioning

confidence: 99%

“…The reference term can be treated under the local density approximation (LDA) or a weighted-density approximation (WDA) 1,39 . Several authors have proposed different functions and approaches [63][64][65][66][67][68][69][70][71] , including those that incorporate correlations in the perturbative contribution [71][72][73][74][75] following similar ideas to those originally proposed by Toxvaerd [76][77][78] .…”

Section: Introductionmentioning

confidence: 99%

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Vapour–liquid interfacial properties of square-well chains from density functional theory and Monte Carlo simulation

Martínez-Ruiz

Blas

Bravo

et al. 2017

Phys. Chem. Chem. Phys.

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The statistical associating fluid theory for attractive potentials of variable range (SAFT-VR) density functional theory (DFT) developed by [Gloor et al., J. Chem. Phys., 2004, 121, 12740-12759] is used to predict the interfacial behaviour of molecules modelled as fully-flexible square-well chains formed from tangentially-bonded monomers of diameter σ and potential range λ = 1.5σ. Four different model systems, comprising 4, 8, 12, and 16 monomers per molecule, are considered. In addition to that, we also compute a number of interfacial properties of molecular chains from direct simulation of the vapour-liquid interface. The simulations are performed in the canonical ensemble, and the vapour-liquid interfacial tension is evaluated using the wandering interface (WIM) method, a technique based on the thermodynamic definition of surface tension. Apart from surface tension, we also obtain density profiles, coexistence densities, vapour pressures, and critical temperature and density, paying particular attention to the effect of the chain length on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapour-liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the surface tension increases as the molecular chains get longer. The interfacial thickness and surface tension appear to exhibit an asymptotic limiting behaviour for long chains. A similar behaviour is also observed for the coexistence densities and critical properties. Agreement between theory and simulation results indicates that SAFT-VR DFT is only able to predict qualitatively the interfacial properties of the model. Our results are also compared with simulation data taken from the literature, including the vapour-liquid coexistence densities, vapour pressures, and surface tension.

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Section: Model and Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vapour–liquid interfacial properties of square-well chains from density functional theory and Monte Carlo simulation

Martínez-Ruiz

Blas

Bravo

et al. 2017

Phys. Chem. Chem. Phys.

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“…Theoretically, DFT is applicable to both bulk and interfacial problems in a self-consistent manner. Various versions of DFT have been used to investigate the interfacial phenomena of model and real fluids containing polar and neutral substances, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] polymers, [19][20][21][22] colloids, [23][24][25] electrolytes, 26 surfactants, [27][28][29][30][31][32] liquid crystals, 33 and lipid bilayers. 34 However, for the real systems of our particular interest reservoirlike fluids consisting of hydrocarbons, N 2 , CO 2 , H 2 S, and sometimes water, DFT at the current stage only exhibits very limited success especially in application to mixtures.…”

Section: Interfacial Tension Of Nonassociating Pure Substances and Bimentioning

confidence: 99%

Interfacial tension of nonassociating pure substances and binary mixtures by density functional theory combined with Peng–Robinson equation of state

Liu¹,

Firoozabadi²

2009

The Journal of Chemical Physics

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We develop a density functional theory and investigate the interfacial tension of several pure substances N(2), CO(2), H(2)S, normal alkanes from C(1) to nC(10), and binary mixtures C(1)/C(3), C(1)/nC(5), C(1)/nC(7), C(1)/nC(10), CO(2)/nC(4), N(2)/nC(5), N(2)/nC(6), N(2)/nC(8), N(2)/nC(10), nC(6)/nC(7), nC(6)/nC(8), and nC(6)/nC(10). The theory is combined with the semiempirical Peng-Robinson equation of state (PR-EOS). The weighted density approximation (WDA) is adopted to extend the bulk excess Helmholtz free energy to the inhomogeneous interface. Besides, a supplementary term, quadratic density expansion (QDE), is introduced to account for the long-range characteristic of intermolecular dispersion attractions, which cannot be accurately described by the WDA. In the bulk limit, the QDE vanishes and the theory is reduced to the PR-EOS. For pure substances, the potential expansion parameter is the only adjustable parameter in the QDE and determined by using a single measured interfacial tension at the lowest temperature examined. Then without any parameter adjustment, we faithfully predict the interfacial tensions of pure substances and mixtures over a wide range of conditions.

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“…The repulsive potential u 0 (r 12 ) is then approximated by that of an equivalent hard sphere fluid with the diameter d chosen according to the Barker-Henderson prescription [42] For the hard sphere system we use the Carnahan-Starling equation of state. The WCA-type potential separation was successfully applied in all previous simple fluid DFT calculations [14,25,43,44] and it has proven to yield a rather accurate first-order perturbation term to the Helmholtz free energy. Thus there is no need for an attractive second-order term which would considerably complicate the DFT model.…”

Section: Interaction Potential Modelmentioning

confidence: 99%

Modified PT-LJ-SAFT Density Functional Theory

Kahl

Winkelmann

2008

Fluid Phase Equilibria

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Prediction of internal structure and properties in fluid model interfaces of binary and ternary liquid mixtures

Cited by 10 publications

References 63 publications

Vapour–liquid interfacial properties of square-well chains from density functional theory and Monte Carlo simulation

Vapour–liquid interfacial properties of square-well chains from density functional theory and Monte Carlo simulation

Interfacial tension of nonassociating pure substances and binary mixtures by density functional theory combined with Peng–Robinson equation of state

Modified PT-LJ-SAFT Density Functional Theory

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