Inhomogeneous Monte Carlo simulation of the vapor-liquid equilibrium of benzene between 300 K and 530 K

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.

Section: Effective Long-range Pairwise Corrections For the Pressumentioning

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

“…This disagreement follows from neglecting the Lennard-Jones interactions beyond the cut-off distance, R c = 9 Å, and is comparable with the difference observed for nonpolar fluids. [70][71][72] The course of site-site distribution functions between the oxygen atoms (upper part) and between oxygen and hydrogen atoms (lower part) of the hydroxyl groups is shown in Figure 4 for different alcohols at temperature T = 300 K. For the sake of clarity, only the curves for ethanol, butanol, and octanol are plotted. The thin (increasing) lines of corresponding type and colour show the average number of sites of type B up to given separation r from site A,…”

Section: Figmentioning

confidence: 99%

Size distribution of associated clusters in liquid alcohols: Interpretation of simulation results in the frame of SAFT approach

Janeček

Paricaud

2013

The size distribution and topology of associated clusters for primary alcohols is studied using molecular dynamics simulations. Liquid ethanol, propanol, butanol, hexanol, and octanol are simulated at pressure P = 1 bar and temperatures T = 300 K, T = 350 K, and T = 400 K. The fractions of molecules with different sets of hydrogen bonded partners, the size of associated cluster and the site-site distribution functions between atoms participating on hydrogen bonding are extracted from simulated trajectories. For all alcohols longer than ethanol, the length of the alkyl chain has only a marginal effect on the association. Consequently, related properties like coordination numbers of hydroxyl group, size distribution of associates, or fractions of differently coordinated alcohol molecules are independent on the molecular size. Although we employed a force-field without involved polarizability, we observe a positive cooperativity of hydrogen bonding simply as a consequence of steric and electrostatic interactions. The size and topology of associates is analyzed within the frame of 3B model of statistical association fluid theory. Although this approach enables good thermodynamic description of systems containing associating compounds, several insufficiencies appear in the description at molecular level. © 2013 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4827107]

“…In most cases, the simulations use two-body Lennard-Jones site-site potentials and partial charges. These pair potentials have been shown to be successful in reproducing the temperature dependence of the surface tension of various organic liquids, [1][2][3][4][5][6][7][8][9][10][11][12] water, [13][14][15] and acid gases. [16][17][18][19] Although, the surface tension, γ of the simple Lennard-Jones liquid was the first to be studied, 20 the agreement between the simulated surface tension and the experimental results for liquid argon is poor (see Fig.…”

Section: Introductionmentioning

confidence: 99%

The gas-liquid surface tension of argon: A reconciliation between experiment and simulation

Goujon

Malfreyt

Tildesley

2014

We present a simulation of the liquid-vapor interface of argon with explicit inclusion of the three-body interactions. The three-body contributions to the surface tension are calculated using the Kirkwood-Buff approach. Monte Carlo calculations of the long-range corrections to the three-body contribution are calculated from the radial distribution function g((2))(z1, cos θ12, r12). Whereas the effective two-body potentials overestimate the surface tension by more than 15%, the inclusion of the three-body potential provides an excellent agreement with the experimental results for temperatures up to 15 K below the critical temperature. We conclude that the three-body interactions must be explicitly included in accurately modelling the surface tension of argon.