Effect of dispersion forces on the capillary-wave fluctuations of liquid surfaces

Chacón, Enrique; Fernández, Eva M.; Tarazona, P.

doi:10.1103/physreve.89.042406

Cited by 15 publications

(18 citation statements)

References 39 publications

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“…However, γ(q) is expected to not change qualitatively once r c is sufficiently large (q 2π/r c ). From recent simulations of LJ fluids, a shallow minimum near q min ≈ 0.24σ (b ≈ 2.5σ) has indeed been identified within a suitable extrapolation scheme for r c → ∞ [25]. This is not accessible from our data.…”

Section: Definition Of γ(Q)-mentioning

confidence: 63%

Enhanced wavelength-dependent surface tension of liquid-vapour interfaces

Höfling¹,

Dietrich²

2015

EPL

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Due to the simultaneous presence of bulk-like and interfacial fluctuations the understanding of the structure of liquid-vapour interfaces poses a long-lasting and ongoing challenge for experiments, theory, and simulations. We provide a new analysis of this topic by combining high-quality simulation data for Lennard-Jones fluids with an unambiguous definition of the wavenumber-dependent surface tension γ(q) based on the two-point correlation function of the fluid. Upon raising the temperature, γ(q) develops a maximum at short wavelengths. We compare these results with predictions from density functional theory. Our analysis has repercussions for the interpretation of grazing-incidence small-angle X-ray scattering (GISAXS) at liquid interfaces.

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Section: Definition Of γ(Q)-mentioning

confidence: 63%

Enhanced wavelength-dependent surface tension of liquid-vapour interfaces

Höfling¹,

Dietrich²

2015

EPL

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“…The inclusion of long-range dispersion forces (not-truncated LJ interactions) would provide an even more realistic view of the system and add some new qualitative elements. These problems had already been partially addressed with the ISM analysis of computer simulation for the effects of the wall-fluid [26] and in the liquid-vapor interface [24], and the route to their study within the methodology used here appears to be open. The method could also be applied to rough substrates [32], allowing for a nonzero mean amplitude of the film thickness ξ q following the corrugations of the substrate, as well as to more complex fluids and mixtures, to address the complex phenomenology of these important interfacial systems.…”

Section: Discussionmentioning

confidence: 99%

“…This is in agreement with the densityfunctional analysis for any system with truncated or shortrange interactions. Only for long-ranged interactions between the fluid molecules [24,25] or between the wall and the fluid [26,27] we expect that the asymptotic functional form of (ξ ) deviates from Eq. (4), but still it was surprising to observe that, in a realistic model with strong layering effects in the density profiles, the pure exponential decay could give such accurate representation of (ξ ), even for very thin films of just one or two molecular layers.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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We use Monte Carlo simulations of a Lennard-Jones fluid adsorbed on a short-range planar wall substrate to study the fluctuations in the thickness of the wetting layer, and we get a quantitative and consistent characterization of their mesoscopic Hamiltonian, H [ξ ]. We have observed important finite-size effects, which were hampering the analysis of previous results obtained with smaller systems. The results presented here support an appealing simple functional form for H[ξ ], close but not exactly equal to the theoretical nonlocal proposal made on the basis a generic density-functional analysis by Parry and coworkers. We have analyzed systems under different wetting conditions, as a proof of principle for a method that provides a quantitative bridge between the molecular interactions and the phenomenology of wetting films at mesoscopic scales.

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“…The double integral over the pair interactions makes this functional less amenable to analytical calculations, but, more importantly, implies the need to introduce a wave-vector dependent surface tension, 28,30,32,72 as we shall see shortly.…”

Section: Long Range Forces and An Adsorbing Wallmentioning

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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Effect of dispersion forces on the capillary-wave fluctuations of liquid surfaces

Cited by 15 publications

References 39 publications

Enhanced wavelength-dependent surface tension of liquid-vapour interfaces

Enhanced wavelength-dependent surface tension of liquid-vapour interfaces

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

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

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