Evaluation of the contact angle from molecular simulations

Škvára, Jiří; Škvor, Jiřı́; Nezbeda, Ivó

doi:10.1080/08927022.2017.1359744

Cited by 13 publications

(5 citation statements)

References 30 publications

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“…However, a number of studies have recently shown that θ extracted from the geometry of such cylindrical droplets nevertheless depends on the curvature of the droplet [24][25][26] . In addition to the challenges posed by line tension and finite size effects, the determination of θ from droplet geometry is also plagued by a certain degree of ambiguity regarding the exact location of the solid-fluid interface [27][28][29] .…”

Section: A Introductionmentioning

confidence: 99%

Characterizing surface wetting and interfacial properties using enhanced sampling (SWIPES)

et al. 2019

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We introduce an accurate and efficient method for characterizing surface wetting and interfacial properties, such as the contact angle made by a liquid droplet on a solid surface, and the vapor-liquid surface tension of a fluid. The method makes use of molecular simulations in conjunction with the indirect umbrella sampling technique to systematically wet the surface and estimate the corresponding free energy. To illustrate the method, we study the wetting of a family of Lennard-Jones surfaces by water. We estimate contact angles for surfaces with a wide range of attractions for water by using our method and also by using droplet shapes. Notably, as surface -water attractions are increased, our method is able to capture the transition from partial to complete wetting. Finally, the method is straightforward to implement and computationally efficient, providing accurate contact angle estimates in roughly 5 nanoseconds of simulation time. A. IntroductionWetting of solid surfaces by fluids is important in diverse disciplines, including but not limited to surface chemistry, materials characterization, oil and gas recovery 1-5 . In general, the wettability of a solid by a fluid is characterized by a wetting coefficient, k ≡ (γ SV − γ SL )/γ VL , where γ represents surface tension, and the subscripts correspond to the coexisting vapor (V), liquid (L) and solid (S) phases. The wetting coefficient is also related to the contact angle (θ ) that a liquid droplet (surrounded by its vapor) makes with a solid surface; according to Young's equation, cos θ = (γ SV − γ SL )/γ VL = k. Thus, the extent to which a fluid prefers to wet a solid, or the preference of the solid for the

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Section: A Introductionmentioning

confidence: 99%

Characterizing surface wetting and interfacial properties using enhanced sampling (SWIPES)

et al. 2019

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“…Another wetting metric that can be obtained here includes the curvature, which is given by the inverse of the radius of the fitted spherical cap. Alternative procedures for evaluating the contact angles have been presented before in the literature [55,62,93,94].…”

Section: Computation Of the Apparent Contact Anglesmentioning

confidence: 99%

“…The Wenzel [57,58] and Cassie-Baxter [59,60] models, for instance, are expected to be accurate when the drops are much larger than the surface defects [1]. Other wettability metrics include contact line curvature, which can be linked nonlinearly to the contact angles depending on the level of heterogeneity of the surface [61]; interface sensing, which uses the local number density to define the liquid-vapor interfaces [55,62]; and adsorption energy [63]. The wettability can also be quantified thermodynamically via the Young equation or its derived forms [53,54,64,65].…”

Section: Introductionmentioning

confidence: 99%

Surrogate Models for Studying the Wettability of Nanoscale Natural Rough Surfaces Using Molecular Dynamics

et al. 2020

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A molecular modeling methodology is presented to analyze the wetting behavior of natural surfaces exhibiting roughness at the nanoscale. Using atomic force microscopy, the surface topology of a Ketton carbonate is measured with a nanometer resolution, and a mapped model is constructed with the aid of coarse-grained beads. A surrogate model is presented in which surfaces are represented by two-dimensional sinusoidal functions defined by both an amplitude and a wavelength. The wetting of the reconstructed surface by a fluid, obtained through equilibrium molecular dynamics simulations, is compared to that observed by the different realizations of the surrogate model. A least-squares fitting method is implemented to identify the apparent static contact angle, and the droplet curvature, relative to the effective plane of the solid surface. The apparent contact angle and curvature of the droplet are then used as wetting metrics. The nanoscale contact angle is seen to vary significantly with the surface roughness. In the particular case studied, a variation of over 65° is observed between the contact angle on a flat surface and on a highly spiked (Cassie–Baxter) limit. This work proposes a strategy for systematically studying the influence of nanoscale topography and, eventually, chemical heterogeneity on the wettability of surfaces.

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“…For each cluster we selected coordinates of atoms located on the surface and fitted the resulting profiles with the following surface equation [51,52]:…”

Section: Resultsmentioning

confidence: 99%

Soft landing of metal clusters on graphite: a molecular dynamics study

Verkhovtsev,

Erofeev,

Solov'yov

2020

Preprint

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Structure and stability of 3 nm size Ag887, Au887 and Ti787 clusters deposited on graphite under soft landing conditions (∼ 10 −3 − 10 0 eV per atom) are studied by means of molecular dynamics simulations. Parameters for the cluster-surface interaction are derived from complementary ab initio calculations. We found that the shape of clusters on the surface is governed by their elemental composition and depends also on the initial cluster structure and landing conditions. At deposition energies below 0.1 eV/atom, the Ag887 cluster acquires an ellipsoidal shape, while Au887 and Ti787 clusters transform into oblate and prolate truncated spheroids, respectively, due to stronger adhesion to graphite. The clusters flatten over the surface and eventually disintegrate as the deposition energy increases. Simulation results reveal that Ag887 and Au887 fragment at about 0.75 − 1.0 eV/atom whereas higher energy of about 3 eV/atom is required for the fragmentation of Ti787. The contact angle, contact radius and height of the clusters as functions of deposition energy are determined from fitting the positions of cluster surface atoms with a surface equation. The dependence of these parameters on internal energy of the clusters is also analyzed.

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Evaluation of the contact angle from molecular simulations

Cited by 13 publications

References 30 publications

Characterizing surface wetting and interfacial properties using enhanced sampling (SWIPES)

Characterizing surface wetting and interfacial properties using enhanced sampling (SWIPES)

Surrogate Models for Studying the Wettability of Nanoscale Natural Rough Surfaces Using Molecular Dynamics

Soft landing of metal clusters on graphite: a molecular dynamics study

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