Molecular Dynamics Simulations on the Interface between Titanium Dioxide and Water Droplets: A New Model for the Contact Angle

In this work, a tool for estimating the contact angle from the molecular dynamics simulations is developed and presented. The tool (Achilles) can detect water droplet on hydrophobic and hydrophilic surfaces. The tool can reconstruct the droplets broken across the periodic boundaries. Further a neighbor density based accurate filter is used to find the droplet liquid vapor interface and a circle is fitted using it after removing the dense layers of water next to solid surface. This fitted circle is solved for contact angle and results are outputted in the form of graphical images and text. The entire content of the internal computations of the tool is broken down into 4 phases and users can monitor the outcomes at every phase through output images. The tool is tested using sample molecular dynamics results of water droplet on hydrophobic and hydrophilic surfaces. We believe this tool can be a good addition to the molecular dynamics simulation community who work on the interfacial physics, droplet evaporation, super hydrophobic surfaces, and wettability etc.

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Molecular Dynamics Simulations of Oil-Water Wetting Models of Organic Matter and Minerals in Shale at the Nanometer Scale

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.18468 ◽

2021 ◽

Vol 21 (1) ◽

pp. 85-97

Author(s):

Zhentao Dong ◽

Haitao Xue ◽

Bohong Li ◽

Shansi Tian ◽

Shuangfang Lu ◽

...

Keyword(s):

Molecular Dynamics ◽

Contact Angle ◽

Organic Matter ◽

Crude Oil ◽

Molecular Dynamics Simulations ◽

Smooth Surface ◽

Dynamics Simulation ◽

Shale Oil ◽

Water Wetting ◽

Dynamics Simulations

Wettability is an important physical property of shale. This parameter is related to the shale material composition and the fluid properties in the shale pores and plays an important role in the exploration and development of shale oil. Wettability is affected by the scale and roughness. The contact angle at the nanoscale on a smooth surface can better reflect the wettability of shale than the contact angle at higher scales. Molecular dynamics simulations can be used to measure the contact angle on a smooth surface at the nanoscale. This paper focuses on the effects of organic matter and minerals in shale and different components of shale oil on shale wettability. Wetting models of “organic matter-oil component-water,” “quartz-oil component-water” and “kaolinite-oil component-water” at the nanoscale were constructed. Molecular dynamics simulation was used to study the morphological changes of different oil components and water on different surfaces. Studies have shown that organic matter is strongly oleophilic and hydrophobic. Polar components in shale oil can make organic matter slightly hydrophilic. It was recognized by quartz wettability experiments and simulation methods at the nanoscale that the cohesive energy of a liquid has a significant influence on the degree of spreading of the liquid on the surface. The “liquid–liquid–solid” wettability experiment is an effective method for determining mineral oleophilic or hydrophilic properties. The nanoquartz in the shale is strongly hydrophilic. The water wetting angle is related to the crude oil component. Nanokaolinite can have a tetrahedral or an octahedral surface; the tetrahedral surface is oleophilic and hydrophobic, and the octahedral surface exhibits strong hydrophilicity. The wettabilities of both surfaces are related to the crude oil component.

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Glycine in aerosol water droplets: a critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-519-2011 ◽

2011 ◽

Vol 11 (2) ◽

pp. 519-527 ◽

Cited By ~ 19

Author(s):

X. Li ◽

T. Hede ◽

Y. Tu ◽

C. Leck ◽

H. Ågren

Keyword(s):

Molecular Dynamics ◽

Surface Tension ◽

Molecular Dynamics Simulations ◽

Global Climate ◽

Pure Water ◽

Model Systems ◽

Water Droplets ◽

Cloud Droplets ◽

Kohler Theory ◽

Dynamics Simulations

Abstract. Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Köhler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems, the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Köhler equation could be improved by incorporating surface tension corrections.

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