Oscillatory behavior of nanodroplets

Arcidiacono, S.; Poulikakos, Dimos; Ventikos, Yiannis

doi:10.1103/physreve.70.011505

Cited by 21 publications

(16 citation statements)

References 23 publications

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“…The intrinsic width obtained in the MDS of monatomic LJ model fluids (when the model LJ interaction potential of the particles was very close to that measured experimentally, for example between argon atoms) was found to be in very good agreement with that estimated from experiments. 21,[23][24][25] Similar values of the intrinsic width were reported for the liquid-gas interfaces of carbon tetrachloride, water, alkanes and alcohols. 25 Therefore, it is difficult at the moment to expect, at least for simple interfaces, that the relaxation times of the surface phase would be on the time scale required by the IFT.…”

Section: Introductionsupporting

confidence: 74%

Hydrodynamics of Moving Contact Lines: Macroscopic versus Microscopic

Lukyanov

Pryer

2017

Langmuir

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The fluid-mechanics community is currently divided in assessing the boundaries of applicability of the macroscopic approach to fluid mechanical problems. Can the dynamics of nanodroplets be described by the same macroscopic equations as the ones used for macro-droplets? To the greatest degree, this question should be addressed to the moving contact-line problem. The problem is naturally multiscale, where even using a slip boundary condition results in spurious numerical solutions and transcendental stagnation regions in modelling in the vicinity of the contact line. In this publication, it has been demonstrated via the mutual comparison between macroscopic modelling and molecular dynamics simulations that a small, albeit natural, change in the boundary conditions is all that is necessary to completely regularize the problem and eliminate these nonphysical effects. The limits of macroscopic approach applied to the moving contact-line problem have been tested and validated from the first microscopic principles of molecular dynamic simulations.

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Section: Introductionsupporting

confidence: 74%

Hydrodynamics of Moving Contact Lines: Macroscopic versus Microscopic

Lukyanov

Pryer

2017

Langmuir

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“…This effect of the capillary wave motion has been clearly observed and studied in MD simulations and in the experiments on simple fluids [8,36,48,49,[51][52][53][54][55]. In particular, MD simulations of nanoscale capillary waves (with amplitude ≈ 0.3 particle diameters) in liquid argon drops have decisively demonstrated that capillary wave motion closely follows predictions of continuum hydrodynamics (frequency and damping coefficient), the observed temperature dependence of the density profile width is in a very good agreement with experiments on liquid argon [51,52]. The width of the density profile was found to be within 1.…”

Section: A the Density Profile In Monatomic Lj Liquid Dropsmentioning

confidence: 81%

Relaxation of surface tension in the free-surface boundary layer of simple Lennard-Jones liquids

Lukyanov

Likhtman

2013

The Journal of Chemical Physics

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In this paper we use molecular dynamics to answer a classical question: how does the surface tension on a liquid/gas interface appear? After defining surface tension from the first principles and performing several consistency checks, we perform a dynamic experiment with a single simple liquid nanodroplet. At time zero, we remove all molecules of the interfacial layer, creating a fresh bare interface with the bulk arrangement of molecules. After that the system evolves towards equilibrium, and the expected surface tension is re-established. We found that the system relaxation consists of three distinct stages. First, the mechanical balance is quickly re-established. During this process the notion of surface tension is meaningless. In the second stage, the surface tension equilibrates, and the density profile broadens to a value which we call "intrinsic" interfacial width. During the third stage, the density profile continues to broaden due to capillary wave excitations, which does not however affect the surface tension. We have observed this scenario for monatomic Lennard-Jones (LJ) liquid as well as for binary LJ mixtures at different temperatures, monitoring a wide range of physical observables.

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“…[53,55,62,78]) for drops of up to ∼ 8 × 10 5 LJ particles corresponding to radii of almost 100 diameters [62]. It is also very clear that the fluid drops experience large fluctuations in shape and size, particularly in the case of large systems, as has been shown by Arcidiacono et al [61] and Salonen et al [64]. With a thermodynamic approach based on a linear response of the free energy to small volume perturbations, El Bardouni et al [55] reported some values of the tension for spherical and cylindrical surfaces that are larger than the planar limit (corresponding to δ < 0), though the uncertainty is such that they concluded that the tension is essentially curvature independent.…”

Section: Introductionmentioning

confidence: 75%

A perspective on the interfacial properties of nanoscopic liquid drops

Malijevský

Jackson

2012

J. Phys.: Condens. Matter

103

113

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The structural and interfacial properties of nanoscopic liquid drops are assessed by means of mechanical, thermodynamical, and statistical mechanical approaches that are discussed in detail, including original developments at both the macroscopic level and the microscopic level of density functional theory (DFT). With a novel analysis we show that a purely macroscopic (static) mechanical treatment can lead to a qualitatively reasonable description of the surface tension and the Tolman length of a liquid drop; the latter parameter, which characterizes the curvature dependence of the tension, is found to be negative and has a magnitude of about a half of the molecular dimension. A mechanical slant cannot, however, be considered satisfactory for small finite-size systems where fluctuation effects are significant. From the opposite perspective, a curvature expansion of the macroscopic thermodynamic properties (density and chemical potential) is then used to demonstrate that a purely thermodynamic approach of this type cannot in itself correctly account for the curvature correction of the surface tension of liquid drops. We emphasize that any approach, e.g., classical nucleation theory, which is based on a purely macroscopic viewpoint, does not lead to a reliable representation when the radius of the drop becomes microscopic. The description of the enhanced inhomogeneity exhibited by small drops (particularly in the dense interior) necessitates a treatment at the molecular level to account for finite-size and surface effects correctly. The so-called mechanical route, which corresponds to a molecular-level extension of the macroscopic theory of elasticity and is particularly popular in molecular dynamics simulation, also appears to be unreliable due to the inherent ambiguity in the definition of the microscopic pressure tensor, an observation which has been known for decades but is frequently ignored. The union of the theory of capillarity (developed in the nineteenth century by Gibbs and then promoted by Tolman) with a microscopic DFT treatment allows for a direct and unambiguous description of the interfacial properties of drops of arbitrary size; DFT provides all of the bulk and surface characteristics of the system that are required to uniquely define its thermodynamic properties. In this vein, we propose a non-local mean-field DFT for Lennard-Jones (LJ) fluids to examine drops of varying size. A comparison of the predictions of our DFT with recent simulation data based on a second-order fluctuation analysis (Sampayo et al 2010 J. Chem. Phys. 132 141101) reveals the consistency of the two treatments. This observation highlights the significance of fluctuation effects in small drops, which give rise to additional entropic (thermal non-mechanical) contributions, in contrast to what one observes in the case of planar interfaces which are governed by the laws of mechanical equilibrium. A small negative Tolman length (which is found to be about a tenth of the molecular diameter) and a non-monotonic behaviour of the surf...

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Oscillatory behavior of nanodroplets

Cited by 21 publications

References 23 publications

Hydrodynamics of Moving Contact Lines: Macroscopic versus Microscopic

Hydrodynamics of Moving Contact Lines: Macroscopic versus Microscopic

Relaxation of surface tension in the free-surface boundary layer of simple Lennard-Jones liquids

A perspective on the interfacial properties of nanoscopic liquid drops

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