Intrinsic profiles and the structure of liquid surfaces

Tarazona, P.; Chacón, Enrique; Bresme, Fernando

doi:10.1088/0953-8984/24/28/284123

Cited by 31 publications

(53 citation statements)

References 50 publications

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“…Therefore, the bending rigidity κ, which weights the curvature contribution to the surface Hamiltonian H[ξ ], is also dependent on the specific definition for the IS. 32,35 Any experimental measurement, theoretical prediction, or computer simulation evaluation of κ is as good as the definition of ξ (R) that is behind it.…”

Section: Discussion Of the Definition Of The Intrinsic Surfacementioning

confidence: 99%

Capillary wave spectrum at adsorbed liquid films

2012

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Capillary wave fluctuations at the edges of liquid wetting layers are analyzed in Monte Carlo simulations of a Lennard-Jones fluid adsorbed on a planar wall substrate. The analysis is based on the Fourier modes of the liquid surface, constructed via the intrinsic sampling method. For films thinner than four molecular layers we can quantify the damping of the capillary waves due to the wall potential. Our results are presented in the theoretical framework of the effective surface Hamiltonians, to establish a quantitative link between the molecular structure and the mesoscopic descriptions used for renormalization-group analysis. We observe the predicted exponential decay of the wall damping, with the correlation length of the liquid bulk. However, associated with the molecular layering of the density profiles, we observe a strong oscillatory dependence with respect to the mean film thickness, not included in any theoretical prediction. We discuss the possibility of finite-size effects in this respect. Three different definitions of the intrinsic surface at molecular level are tested, to show that the square gradient terms of the Hamiltonian are robust, while the surface bending (or nonlocal) terms are tied to each specific definition.

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Section: Discussion Of the Definition Of The Intrinsic Surfacementioning

confidence: 99%

Capillary wave spectrum at adsorbed liquid films

2012

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“…30,31 This approach, and similar ones, [32][33][34] have been applied to a number of fluid interfaces; simple fluids, 35 water, 36,37 alkali fluids, 38 oil-water interfaces, 32, 39-41 hydrophilic interfaces, 42 and molten salts. 43 The intrinsic profile offers a higher level of resolution of the interface, and, unlike the mean profiles, it is independent of the interfacial cross sectional area used in the simulations. Hence, these intrinsic density profiles provide a better reference to compare simulation data with experimental results obtained using spectroscopic techniques.…”

Section: Introductionmentioning

confidence: 99%

The structure of ionic aqueous solutions at interfaces: An intrinsic structure analysis

Bresme

Chacón

Tarazona

et al. 2012

The Journal of Chemical Physics

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We investigate the interfacial structure of ionic solutions consisting of alkali halide ions in water at concentrations in the range 0.2-1.0 molal and at 300 K. Combining molecular dynamics simulations of point charge ion models and a recently introduced computational approach that removes the averaging effect of interfacial capillary waves, we compute the intrinsic structure of the aqueous interface. The interfacial structure is more complex than previously inferred from the analysis of mean profiles. We find a strong alternating double layer structure near the interface, which depends on the cation and anion size. Relatively small changes in the ion diameter disrupt the double layer structure, promoting the adsorption of anions or inducing the density enhancement of small cations with diameters used in simulation studies of lithium solutions. The density enhancement of the small cations is mediated by their strong water solvation shell, with one or more water molecules "anchoring" the ion to the outermost water layer. We find that the intrinsic interfacial electrostatic potential features very strong oscillations with a minimum at the liquid surface that is ∼4 times stronger than the electrostatic potential in the bulk. For the water model employed in this work, SPC/E, the electrostatic potential at the water surface is ∼−2 V, equivalent to ∼80 k B T (for T = 300 K), much stronger than previously considered. Furthermore, we show that the utilization of the intrinsic surface technique provides a route to extract ionic potentials of mean force that are not affected by the thermal fluctuations, which limits the accuracy of most past approaches including the popular umbrella sampling technique.

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“…The non equilibrium approach can potentially be useful in studying the energy of adsorption of more complex structures (e.g. amphiphilic molecules) in liquid-vapour water systems [54,55].…”

Section: Discussionmentioning

confidence: 99%

Nonequilibrium study of the intrinsic free-energy profile across a liquid-vapour interface

Braga

Muscatello

Lau

et al. 2016

The Journal of Chemical Physics

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We calculate an atomistically detailed free-energy profile across a heterogeneous system using a nonequilibrium approach. The path-integral formulation of Crooks fluctuation theorem is used in conjunction with the intrinsic sampling method (ISM) to calculate the free-energy profile for the liquid-vapour interface of the Lennard-Jones fluid. Free-energy barriers are found corresponding to the atomic layering in the liquid phase as well as a barrier associated with the presence of an adsorbed layer as revealed by the intrinsic density profile. Our findings are in agreement with profiles calculated using Widom's potential distribution theorem applied to both the average and the intrinsic profiles as well as literature values for the excess chemical potential.

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Intrinsic profiles and the structure of liquid surfaces

Cited by 31 publications

References 50 publications

Capillary wave spectrum at adsorbed liquid films

Capillary wave spectrum at adsorbed liquid films

The structure of ionic aqueous solutions at interfaces: An intrinsic structure analysis

Nonequilibrium study of the intrinsic free-energy profile across a liquid-vapour interface

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