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

Lukyanov, Alex V.; Likhtman, Alexei E.

doi:10.1063/1.4774690

Cited by 20 publications

(24 citation statements)

References 61 publications

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“…To compare the results of MDS with the macroscopic description (12)-(18), the model parameters Re, Ca, ρ √ ff m f /σ 2 ff and surface tension γ = 0.92 ff /σ 2 ff , calculated as in reference. 19 In our approach here, there is some degree of arbitrariness how one can set apart the interfaces from the bulk. 11,35 To get an estimate for characteristic values of interfacial parameters a minimum cut-off the areas with strong variations of density is applied.…”

Section: Macroscopic Parameters From Mdsmentioning

confidence: 99%

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: Macroscopic Parameters From Mdsmentioning

confidence: 99%

Hydrodynamics of Moving Contact Lines: Macroscopic versus Microscopic

Lukyanov

Pryer

2017

Langmuir

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“…We use this procedure in the case of a relaxation process driven by the chemical potential difference; we follow the time dependence of the spectrum and extract from it an estimate for the effective dynamic tension. This is an alternative to the computation of gradients and anisotropies across the interface, which also define dynamic stiffnesses, such as in the case of composition gradients in Kortweg's theory of effective surface tension, 39 the pressure tensor anisotropy, 18 or non-equilibrium linear response to excitations. 40,41 In the following, we will analyze different relaxation dynamics related to the crystallization of a Lennard-Jones liquid in contact with a crystalline substrate using CWT and fluctuating hydrodynamics in order to extract the dynamic behavior of the crystal-liquid interfacial stiffness that is related to the tension by Eq.…”

Section: Capillary Wave Theory and Stiffnessesmentioning

confidence: 99%

“…There is simulation and experimental evidence that the description of growth phenomena requires the introduction of an effective dynamic tension in order to properly stabilize the interface during the transient states for fluid-fluid interfaces, [12][13][14] but there still is a substantial lack of consensus on the determination of the proper relaxation times related to it and their interpretation. [15][16][17][18] In the present study we concentrate our attention on solid-liquid interfaces and the relaxation process associated with crystallization. As compared to relaxing liquidliquid interfaces, crystal growth poses an additional challenge due to the elastic and viscous properties of the growing, off-equilibrium solid phase.…”

Section: Introductionmentioning

confidence: 99%

Crystal growth from a supersaturated melt: Relaxation of the solid-liquid dynamic stiffness

Turci

Schilling

2014

The Journal of Chemical Physics

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A molecular theory of the solid-liquid interface. II. Study of bcc crystal-melt interfaces J. Chem. Phys. 76, 6262 (1982); 10.1063/1.443029 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation. We discuss the growth process of a crystalline phase out of a metastable over-compressed liquid that is brought into contact with a crystalline substrate. The process is modeled by means of molecular dynamics. The particles interact via the Lennard-Jones potential and their motion is locally thermalized by Langevin dynamics. We characterize the relaxation process of the solid-liquid interface, showing that the growth speed is maximal for liquid densities above the solid coexistence density, and that the structural properties of the interface rapidly converge to equilibrium-like properties. In particular, we show that the off-equilibrium dynamic stiffness can be extracted using capillary wave theory arguments, even if the growth front moves fast compared to the typical diffusion time of the compressed liquid, and that the dynamic stiffness converges to the equilibrium stiffness in times much shorter than the diffusion time. © 2014 AIP Publishing LLC. [http://dx

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“…The obtained values of θ 0 were found to be within 3 • of the contact angles calculated directly from the Young-Dupree equation using independently evaluated values of the surface tensions. The liquid-gas γ LV surface tension has been calculated using large liquid drops (radius ∼ 30), similar to [26]. Typical dependencies of the integrand of (2), γ LS (y), in static conditions are shown in Figs.…”

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confidence: 99%

Relaxation of Surface Tension in the Liquid–Solid Interfaces of Lennard-Jones Liquids

Lukyanov

Likhtman

2013

Langmuir

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We have established the surface tension relaxation time in the liquid-solid interfaces of LennardJones (LJ) liquids by means of direct measurements in molecular dynamics (MD) simulations. The main result is that the relaxation time is found to be weakly dependent on the molecular structures used in our study and lies in such a range that in slow hydrodynamic motion the interfaces are expected to be at equilibrium. The implications of our results for the modelling of dynamic wetting processes and interpretation of dynamic contact angle data are discussed.The wetting of solid materials by a liquid is at the heart of many industrial processes and natural phenomena. The main difficulty in theoretical description and modelling of wetting processes is the formulation of boundary conditions at the moving contact line [1][2][3]. For example, the standard no-slip boundary condition of classical hydrodynamics had to be relaxed to eliminate the well-known non-integrable stress singularity at the contact line [1][2][3][4][5].The principal parameter of the theoretical description is the dynamic contact angle, which is one of the boundary conditions to determine the shape of the free surface [1][2][3]. The notion of the contact angle has two meanings in macroscopic modelling. One is apparent contact angle θ a , which is observed experimentally at some distance from the contact line defined by the resolution of experimental techniques (usually about a few µm) and another one is true contact angle θ right at the contact line. When the contact line is moving, the apparent contact angle deviates from its static values and becomes a function of velocity. For example, quite often the contactangle-velocity dependence θ a (U ) observed in experiments can be accurately described bywhere a 1 , a 2 are material parameters depending on temperature and properties of the liquid-solid combination, U is the contact-line velocity and θ 0 is the static contact angle [3]. However useful relationship (1) may be, it is neither general, due to the well known effects of nonlocality [6,7], nor it can be directly used in macroscopic modelling since it is the true contact angle which enters the boundary conditions used in macroscopic analysis. While the apparent contact angle can be experimentally observed, the true contact angle can be only inferred from theoretical considerations or from microscopic modelling such as MD simulations. This is the one of the main fundamental problems of wetting hydrodynamics, and that problem, despite decades of research, is still far from a complete understanding. The main question still remains open and debates continue: how (and why) does the true dynamic contact angle change with the contact-line velocity?The simple hypothesis that θ = θ 0 has been used in the so-called hydrodynamic theories, for example [8], where the experimentally observed changes in the apparent contact angle were attributed to viscous bending of the free surface in a mesoscopic region near the contact line. Some early observations of the menis...

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

Cited by 20 publications

References 61 publications

Hydrodynamics of Moving Contact Lines: Macroscopic versus Microscopic

Hydrodynamics of Moving Contact Lines: Macroscopic versus Microscopic

Crystal growth from a supersaturated melt: Relaxation of the solid-liquid dynamic stiffness

Relaxation of Surface Tension in the Liquid–Solid Interfaces of Lennard-Jones Liquids

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