Mesoscopic Hamiltonian for the fluctuations of adsorbed Lennard-Jones liquid films

Fernández, Eva M.; Chacón, Enrique; MacDowell, Luis G.; Tarazona, P.

doi:10.1103/physreve.91.062404

Cited by 4 publications

(6 citation statements)

References 33 publications

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“…The progress made in Refs. [7,13,14] was to develop a DFT based method for calculating g(h), or strictly speaking g(Γ), that is valid over the whole range of values of h. Note that one can also use a molecular dynamics computer simulation based method for calculating g(h) [33][34][35][36][37]. For simple Lennard-Jones like fluids it was shown [7,13,14] that the following form gives a good fit to the binding potential over the whole range:…”

Section: Wetting Behaviour and The Form Of The Binding Potentialmentioning

confidence: 99%

“…(a) The final equilibrium state obtained for the same volume of liquid on the surface undergoing both spreading and dewetting on a background film h = h0. The binding potential used is g2, with initial conditions that were evolved to reach these final equilibria given in(37) for the spreading situation, and (38) for dewetting. (b) shows the corresponding evolutions of the normalised free energy differences, noting that for spreading F (0) = 16.89 and F (∞) = 0.046, whereas for dewetting F (0) = 0.44 and F (∞) = 0.15.…”

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confidence: 99%

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Films, layers, and droplets: The effect of near-wall fluid structure on spreading dynamics

et al. 2017

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We present a study of the spreading of liquid droplets on a solid substrate at very small scales. We focus on the regime where effective wetting energy (binding potential) and surface tension effects significantly influence steady and spreading droplets. In particular, we focus on strong packing and layering effects in the liquid near the substrate due to underlying density oscillations in the fluid caused by attractive substrate-liquid interactions. We show that such phenomena can be described by a thin-film (or long-wave or lubrication) model including an oscillatory Derjaguin (or disjoining or conjoining) pressure and explore the effects it has on steady droplet shapes and the spreading dynamics of droplets on both an adsorption (or precursor) layer and completely dry substrates. At the molecular scale, commonly used two-term binding potentials with a single preferred minimum controlling the adsorption layer height are inadequate to capture the rich behavior caused by the near-wall layered molecular packing. The adsorption layer is often submonolayer in thickness, i.e., the dynamics along the layer consists of single-particle hopping, leading to a diffusive dynamics, rather than the collective hydrodynamic motion implicit in standard thin-film models. We therefore modify the model in such a way that for thicker films the standard hydrodynamic theory is realized, but for very thin layers a diffusion equation is recovered.

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Section: Wetting Behaviour and The Form Of The Binding Potentialmentioning

confidence: 99%

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confidence: 99%

Films, layers, and droplets: The effect of near-wall fluid structure on spreading dynamics

et al. 2017

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“…Theoretical studies on this topic indicate that the substrate distorts the liquidvapor profile, 40,41 and therefore conveys a film height dependence to the surface tension (also known as position dependent stiffness) of which there are currently strong indications from computer simulations. 42,43 Recently, we studied the interface fluctuations of an adsorbed film in the presence of a long range external field. [44][45][46] In this case, the liquid-vapor interface feels the substrate directly via the long range forces, rather than indirectly, via weak substrate-fluid correlations.…”

Section: Introductionmentioning

confidence: 99%

Capillary wave theory of adsorbed liquid films and the structure of the liquid-vapor interface

MacDowell

2017

Phys. Rev. E

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In this paper we try to work out in detail the implications of a microscopic theory for capillary waves under the assumption that the density is given along lines normal to the interface. Within this approximation, which may be justified in terms of symmetry arguments, the Fisk-Widom scaling of the density profile holds for frozen realizations of the interface profile. Upon thermal averaging of capillary wave fluctuations, the resulting density profile yields results consistent with renormalization group calculations in the one-loop approximation. The thermal average over capillary waves may be expressed in terms of a modified convolution approximation where normals to the interface are Gaussian distributed. In the absence of an external field we show that the phenomenological density profile applied to the square-gradient free energy functional recovers the capillary wave Hamiltonian exactly. We extend the theory to the case of liquid films adsorbed on a substrate. For systems with short-range forces, we recover an effective interface Hamiltonian with a film height dependent surface tension that stems from the distortion of the liquid-vapor interface by the substrate, in agreement with the Fisher-Jin theory of short-range wetting. In the presence of long-range interactions, the surface tension picks up an explicit dependence on the external field and recovers the wave vector dependent logarithmic contribution observed by Napiorkowski and Dietrich. Using an error function for the intrinsic density profile, we obtain closed expressions for the surface tension and the interface width. We show the external field contribution to the surface tension may be given in terms of the film's disjoining pressure. From literature values of the Hamaker constant, it is found that the fluid-substrate forces may be able to double the surface tension for films in the nanometer range. The film height dependence of the surface tension described here is in full agreement with results of the capillary wave spectrum obtained recently in computer simulations, and the predicted translation mode of surface fluctuations reproduces to linear order in field strength an exact solution of the density correlation function for the Landau-Ginzburg-Wilson Hamiltonian in an external field.

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“…The connection with the curvature expansion is evident as, taking into account Eqs. (36) and (39), we find that…”

Section: B General Diagrammatic Approachmentioning

confidence: 51%

“…The search for a link between truly microscopic approaches and these mesoscopic descriptions can be traced back to van der Waals [24] and continue to this day, and in the past few years considerable effort has been invested in establishing this connection more rigorously. For example, intrinsic sampling methods use a many-body percolative, approach to identify the interfacial position from the underlying microscopic molecular configurations, and this has been extensively used in simulations [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. A second, related, development has been the attempt to sys-tematically derive an interfacial model for wetting transitions in settings involving short-ranged intermolecular forces from a more microscopic starting point [39][40][41][42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

Curvature corrections to the nonlocal interfacial model for short-ranged forces

Romero-Enrique¹,

Squarcini²,

Parry³

et al. 2018

Phys. Rev. E

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In this paper we revisit the derivation of a nonlocal interfacial Hamiltonian model for systems with short-ranged intermolecular forces. Starting from a microscopic Landau-Ginzburg-Wilson Hamiltonian with a double-parabola potential, we reformulate the derivation of the interfacial model using a rigorous boundary integral approach. This is done for three scenarios: a single fluid phase in contact with a nonplanar substrate (i.e., wall); a free interface separating coexisting fluid phases (say, liquid and gas); and finally a liquid-gas interface in contact with a nonplanar confining wall, as is applicable to wetting phenomena. For the first two cases our approaches identifies the correct form of the curvature corrections to the free energy and, for the case of a free interface, it allows us to recast these as an interfacial self-interaction as conjectured previously in the literature. When the interface is in contact with a substrate our approach similarly identifies curvature corrections to the nonlocal binding potential, describing the interaction of the interface and wall, for which we propose a generalized and improved diagrammatic formulation.

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Mesoscopic Hamiltonian for the fluctuations of adsorbed Lennard-Jones liquid films

Cited by 4 publications

References 33 publications

Films, layers, and droplets: The effect of near-wall fluid structure on spreading dynamics

Films, layers, and droplets: The effect of near-wall fluid structure on spreading dynamics

Capillary wave theory of adsorbed liquid films and the structure of the liquid-vapor interface

Curvature corrections to the nonlocal interfacial model for short-ranged forces

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