Effect of molecular flexibility of Lennard-Jones chains on vapor-liquid interfacial properties

Blas, Felipe J.; Bravo, A. I. Moreno-Ventas; Algaba, Jesús; Martínez-Ruiz, F. J.; MacDowell, Luis G.

doi:10.1063/1.4868100

Cited by 12 publications

(11 citation statements)

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“…In agreement with previous studies on the subject, 34,[80][81][82][83] the results of this work show that the effect of molecular flexibility on the isotropic (vapor-liquid) phase behavior of attractive chain fluids is quite small. If the equation of state is coupled to a suitable description of anisotropic phases (such as solids or liquid crystals), however, it is expected these subtle effects can make the difference for an accurate prediction of phase equilibria (see, for example, Ref.…”

Section: Resultssupporting

confidence: 81%

On the vapor-liquid equilibrium of attractive chain fluids with variable degree of molecular flexibility

Westen

Vlugt

Groß

2015

The Journal of Chemical Physics

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Articles you may be interested inOn the vapor-liquid equilibrium of attractive chain fluids with variable degree of molecular flexibility We study the isotropic (vapor and liquid) phase behavior of attractive chain fluids. Special emphasis is placed on the role of molecular flexibility, which is studied by means of a rod-coil model. Two new equations of state (EoSs) are developed for square-well-(SW) and Lennard-Jones (LJ) chain fluids. The EoSs are developed by applying the perturbation theory of Barker and Henderson (BH) to a reference fluid of hard chain molecules. The novelty of the approach is based on (1) the use of a recently developed hard-chain reference EoS that explicitly incorporates the effects of molecular flexibility, (2) the use of recent molecular simulation data for the radial distribution function of hard-chain fluids, and (3) a newly developed effective segment size, which effectively accounts for the soft repulsion between segments of LJ chains. It is shown that the effective segment size needs to be temperature-, density-, and chain-length dependent. To obtain a simplified analytical EoS, the perturbation terms are fitted by polynomials in density (SW and LJ), chain length (SW and LJ), and temperature (only for LJ). It is shown that the equations of state result in an accurate description of molecular simulation data for vapor-liquid equilibria (VLE) and isotherms of fully flexible SW-and LJ chain fluids and their mixtures. To evaluate the performance of the equations of state in describing the effects of molecular flexibility on VLE, we present new Monte Carlo simulation results for the VLE of rigid linear-and partially flexible SW-and LJ chain fluids. For SW chains, the developed EoS is in a good agreement with simulation results. For increased rigidity of the chains, both theory and simulations predict an increase of the VL density difference and a slight increase of the VL critical temperature. For LJ chains, the EoS proves incapable of reproducing part of these trends. C 2015 AIP Publishing LLC.[http://dx

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Section: Resultssupporting

confidence: 81%

On the vapor-liquid equilibrium of attractive chain fluids with variable degree of molecular flexibility

Westen

Vlugt

Groß

2015

The Journal of Chemical Physics

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“…models with two Lennard-Jones sites and one point quadrupole for oxygen and nitrogen 5 and a model with four Lennard-Jones sites, one point dipole and one point quadrupole for acetone. [9][10][11][12] Here, the implementation by Werth et al 13 was used for molecular interactions exceeding the cutoff radius of 2.2 nm. For each binary mixture, one additional unlike interaction parameter was adjusted to one experimental data point of the vapor pressure or the Henry's law constant, 6,7 thus yielding predictive simulation results of interfacial behavior.…”

Section: Simulationmentioning

confidence: 99%

Fluid phase interface properties of acetone, oxygen, nitrogen and their binary mixtures by molecular simulation

Eckelsbach

Vrabec

2015

Phys. Chem. Chem. Phys.

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Vapor-liquid equilibria (VLE) of the pure substances acetone, oxygen and nitrogen as well as their binary mixtures are studied by molecular dynamics (MD) simulation with a direct approach. Thereby, particular attention is paid to the interface behavior on the molecular level, yielding total and partial density profiles as well as surface tension data. The classical approach by van der Waals is used to analyze the total density profiles. It is found that an extended function is needed to describe those profiles for the mixtures containing acetone, due to the strong adsorption of the volatile component at the vapor side of the interface. Based on these representations the interface thickness is studied. The surface tension results are compared to experimental data, correlations thereof and results from other molecular approaches. Due to the scarcity of experiments, the parachor method is employed to obtain predictive surface tension data for the mixtures. Following the same approach, the present surface tension results are correlated for the mixtures containing acetone.

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“…As mentioned previously, MacDowell and Blas 7 have proposed an improved methodology of the Janeček's 6 method for dealing with the intermolecular interactions of an inhomogeneous system due to LRC. The method, which is simpler and more accurate, elegant, and easier to implement in a simulation code than the original one, has been applied successfully to calculate the interfacial properties of several models, including fully flexible and rigid-linear Lennard-Jones chains 7,[55][56][57] and water and carbon dioxide. 58 Following the recipe of MacDowell and Blas, 7,58 Eq.…”

Section: Effective Long-range Pairwise Corrections For the Pressumentioning

confidence: 99%

“…The number of molecules, N, used in all the simulations performed in this work is constant, N = 2048. As in previous studies, 7,19,39,[55][56][57][58][59] this choice is made so as to have systems with the same total number of molecules. Simulations are performed in the NVT ensemble.…”

Section: Model and Simulation Detailsmentioning

confidence: 99%

Effect of dispersive long-range corrections to the pressure tensor: The vapour-liquid interfacial properties of the Lennard-Jones system revisited

Martínez-Ruiz

Blas

Mendiboure

et al. 2014

The Journal of Chemical Physics

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We propose an extension of the improved version of the inhomogeneous long-range corrections of Janeček [J. Phys. Chem. B 110, 6264-6269 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] to account for the intermolecular potential energy of spherical, rigid, and flexible molecular systems, to deal with the contributions to the microscopic components of the pressure tensor due to the dispersive long-range corrections. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of spherical Lennard-Jones molecules with different cutoff distances, r(c) = 2.5, 3, 4, and 5σ. In addition, we have also considered cutoff distances r(c) = 2.5 and 3σ in combination with the inhomogeneous long-range corrections proposed in this work. The normal and tangential microscopic components of the pressure tensor are obtained using the mechanical or virial route in combination with the recipe of Irving and Kirkwood, while the macroscopic components are calculated using the Volume Perturbation thermodynamic route proposed by de Miguel and Jackson [J. Chem. Phys. 125, 164109 (2006)]. The vapour-liquid interfacial tension is evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the Test-Area methodology. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, vapour pressure, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the cutoff distance and the long-range corrections on these properties. According to our results, the main effect of increasing the cutoff distance (at fixed temperature) is to sharpen the vapour-liquid interface, to decrease the vapour pressure, and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases, the width of the tangential microscopic component of the pressure tensor profile increases, and the surface tension increases as the cutoff distance is larger. We have also checked the effect of the impulsive contribution to the pressure due to the discontinuity of the intermolecular interaction potential when it is cut. If this contribution is not accounted for in the calculation of the microscopic components of the pressure tensor, incorrect values of both components as well as a wrong structure along the vapour-liquid interface are obtained.

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Effect of molecular flexibility of Lennard-Jones chains on vapor-liquid interfacial properties

Cited by 12 publications

References 75 publications

On the vapor-liquid equilibrium of attractive chain fluids with variable degree of molecular flexibility

On the vapor-liquid equilibrium of attractive chain fluids with variable degree of molecular flexibility

Fluid phase interface properties of acetone, oxygen, nitrogen and their binary mixtures by molecular simulation

Effect of dispersive long-range corrections to the pressure tensor: The vapour-liquid interfacial properties of the Lennard-Jones system revisited

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