Perfect wetting along a three-phase line: Theory and molecular dynamics simulations

Abstract

Wetting behavior along a three-phase equilibrium has been obtained by density gradient theory (DGT) and molecular dynamics simulations for a type-II equal size Lennard-Jones mixture. In order to perform a consistent comparison between both methodologies, the molecular parameters of this type of mixture were defined from the global phase diagram of equal size Lennard-Jones mixtures. We have found excellent agreement between predictions from the DGT (coupled to a Lennard-Jones equation for the bulk phases) and simulations results for both the phase and interface behavior, in the whole temperature, pressure, and concentration ranges. For all conditions explored in this work, this type-II mixture shows a three-phase equilibrium composed by a bulk immiscible liquid phase (L1) and a bulk gas phase (G) separated by a second immiscible liquid phase (L2). A similar phase distribution is obtained from the interfacial concentration profile in the whole range of conditions used in this work. This type of structure is a clear evidence that L2 completely wets the GL1 interface. The wetting behavior is also confirmed by the values and evolution of the interfacial tensions. In summary, this kind of type-II mixture does not show wetting transitions and exhibits a permanent perfect wetting in all the thermodynamic conditions explored here.

Modeling ionic liquids and the solubility of gases in them: Recent advances and perspectives

“…We present here new results completing the thermodynamic characterization of these compounds by adding the calculation of their surface tension. In this case, the soft-SAFT Eos is coupled to density gradient theory [169,170], following the work by different authors [165,[171][172][173][174], in order to obtain interfacial properties. The required molecular parameters are those obtained from the density-temperature data, used in a transferable manner, with the additional influence parameter c (see Table 4).…”

Classical density functional theory for the prediction of the surface tension and interfacial properties of fluids mixtures of chain molecules based on the statistical associating fluid theory for potentials of variable range

“…From a more formal perspective, Mejia and Segura 40,41 have studied the interfacial behaviour of Type IV binary mixtures (with regions of both vapour-liquid and liquid-liquid equilibria) by combining DGT with the van der Waals equation of state. This interesting analysis was then extended to the interfacial behaviour exhibited by type I, type II and type V binary mixtures of equal sized Lennard-Jones molecules using a more realistic DGT + soft-SAFT treatment 42,43 , including a comparison with molecular simulation. Kahl and Enders 44,45 were the first to combine a DGT treatment with the SAFT EOS to study the interfacial tension of mixtures of alkanes and of alkanes with methanol.…”

Direct calculation of interfacial properties of fluids close to the critical region by a molecular-based equation of state

“…However, they can be used as a tool to check the accuracy of the approximations made in the theory before applying the model to experimental systems. In this sense, Vega and co-workers [26][27][28] have performed molecular dynamic simulations of Lennard-Jones (LJ) chains and mixtures to test the accuracy of the soft-SAFT equation coupled with DGT for these systems. Their work shows that the theory is very accurate for both, vapor-liquid equilibria and interfacial properties, including interfacial tensions and density profiles, of model pure fluids and binary mixtures and, hence, it can be applied to experimental systems with confidence.…”