Molecular dynamics computer simulations of silica surface structure and adsorption of water molecules

Contact of silver metal surfaces with water, ions and organic ligands experiences induced charges, leading to attractive polarization. These forces play an important role at inorganic/organic interfaces and complement other non-bonded surface interactions. Despite the importance of these interactions, it, however, remains difficult to implement polarization effects to classical molecular dynamics (MD) simulations. In this contribution, we first present an overview of two popular polarizable models, such as Drude oscillator and the rigid rod model, which are utilized to mimic the polarizability of bulk metals. Second, we implemented the rigid rod model to the polarizable force field (FF) for a silver atom, which was further adapted for atomistic MD simulations of silver nanoparticles (AgNPs) composed of 1397 atoms. In our model, induced charge polarization is represented by the displacement of a charge-carrying virtual site attached rigidly to an original Ag atom. To explore the role of polarization, we compared the performance of the classical nonpolarizable FF and the new polarizable model in the MD simulations of adsorption of water and ions onto quasi-spherical AgNP and the flat crystalline silver surface. The analysis of the radial distribution function of Ag-Ag atoms demonstrated that the introduction of the polarization effect had minor effects on face-centered cubic (fcc) packing of silver atoms of bare and water-solvated AgNPs. We found that the polarizable FF causes some increase in attractive interactions between the silver surface and water molecules and Na+ ions. As a crucial test of the developed polarizable model, the structure of adsorbed interfacial water molecules was analyzed. Our data suggest that the environment-induced polarization of the silver surface contributes significantly to the structure of adsorbed interfacial water layers and it also plays an important role in the adsorption of positive ions. However, it was also found out that the polarization effect has a rather short-range effect, so that a minor contribution of silver polarization was seen for adsorption of water molecules and ions from distant solvation shells.

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Structure of the porphyrazine monolayer at the air-water interface: Computer simulation

Pure and Applied Chemistry ◽

10.1351/pac200476010197 ◽

2004 ◽

Vol 76 (1) ◽

pp. 197-202 ◽

Cited By ~ 1

Author(s):

A. Borodin ◽

M. Kiselev

Keyword(s):

Molecular Dynamics ◽

Computer Simulation ◽

Molecular Dynamics Simulations ◽

Computer Simulations ◽

Water Molecules ◽

Water Interface ◽

Air Water Interface ◽

Dynamics Simulations

Molecular dynamics simulations of porphyrazine monolayers at the air-water interface have been carried out. All possible molecular orientations found by analysis of the π-A isotherms are reproduced by computer simulations. The existence of "guest-water" molecules has been observed in the simulation; this confirms the assumptions of experimentalists concerning this phenomenon.

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Adsorption of water molecules on partially oxidized graphite surfaces: a molecular dynamics study of the competition between OH and COOH sites,

Physical Chemistry Chemical Physics ◽

10.1039/b811126j ◽

2008 ◽

Vol 10 (46) ◽

pp. 6998 ◽

Cited By ~ 29

Author(s):

Sylvain Picaud ◽

Barbara Collignon ◽

Paul N. M. Hoang ◽

Jean-Claude Rayez

Keyword(s):

Molecular Dynamics ◽

Water Molecules ◽

Adsorption Of Water ◽

Oxidized Graphite

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A First-Principles Computational Comparison of the Aqueous Anatase TiO2 (001) Interface and the Disordered, Fluorinated TiO2 Interface

10.26434/chemrxiv.7076816.v1 ◽

2018 ◽

Author(s):

Kyle Reeves ◽

Damien Dambournet ◽

Christel Laberty-Robert ◽

Rodolphe Vuilleumier ◽

Mathieu Salanne

Keyword(s):

Density Of States ◽

Density Functional ◽

Water Dissociation ◽

Water Molecules ◽

Chemical Doping ◽

Charge Balance ◽

Functional Theory ◽

Adsorption Of Water ◽

Properties Of Materials ◽

Computational Comparison

Chemical doping and other surface modifications have been used to engineer the bulk properties of materials, but their influence on the surface structure and consequently the surface chemistry are often unknown. Previous work has been successful in fluorinating anatase TiO2 with charge balance achieved via the introduction of Ti vacancies rather than the reduction of Ti. Our work here investigates the interface between this fluorinated titanate with cationic vacancies and a monolayer of water via density functional theory based molecular dynamics. We compute the projected density of states for only those atoms at the interface and for those states that fall within 1eV of the Fermi energy for various steps throughout the simulation, and we determine that the variation in this representation of the density of states serves as a reasonable tool to anticipate where surfaces are most likely to be reactive. In particular, we conclude that water dissociation at the surface is the main mechanism that influences the anatase (001) surface whereas the change in the density of states at the surface of the fluorinated structure is influenced primarily through the adsorption of water molecules at the surface.

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A First-Principles Computational Comparison of the Aqueous Anatase TiO2 (001) Interface and the Disordered, Fluorinated TiO2 Interface

10.26434/chemrxiv.7076816 ◽

2018 ◽

Author(s):

Kyle Reeves ◽

Damien Dambournet ◽

Christel Laberty-Robert ◽

Rodolphe Vuilleumier ◽

Mathieu Salanne

Keyword(s):

Density Of States ◽

Density Functional ◽

Water Dissociation ◽

Water Molecules ◽

Chemical Doping ◽

Charge Balance ◽

Functional Theory ◽

Adsorption Of Water ◽

Properties Of Materials ◽

Computational Comparison

Chemical doping and other surface modifications have been used to engineer the bulk properties of materials, but their influence on the surface structure and consequently the surface chemistry are often unknown. Previous work has been successful in fluorinating anatase TiO2 with charge balance achieved via the introduction of Ti vacancies rather than the reduction of Ti. Our work here investigates the interface between this fluorinated titanate with cationic vacancies and a monolayer of water via density functional theory based molecular dynamics. We compute the projected density of states for only those atoms at the interface and for those states that fall within 1eV of the Fermi energy for various steps throughout the simulation, and we determine that the variation in this representation of the density of states serves as a reasonable tool to anticipate where surfaces are most likely to be reactive. In particular, we conclude that water dissociation at the surface is the main mechanism that influences the anatase (001) surface whereas the change in the density of states at the surface of the fluorinated structure is influenced primarily through the adsorption of water molecules at the surface.

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The Impact of the Electric Field on Surface Condensation of Water Vapor: Insight from Molecular Dynamics Simulation

Nanomaterials ◽

10.3390/nano9010064 ◽

2019 ◽

Vol 9 (1) ◽

pp. 64 ◽

Cited By ~ 7

Author(s):

Qin Wang ◽

Hui Xie ◽

Zhiming Hu ◽

Chao Liu

Keyword(s):

Molecular Dynamics ◽

Water Vapor ◽

Electric Field ◽

Intermolecular Forces ◽

Dynamics Simulation ◽

Water Molecules ◽

Attraction Force ◽

Condensation Rate ◽

Shape Transformation ◽

The Impact

In this study, molecular dynamics simulations were carried out to study the coupling effect of electric field strength and surface wettability on the condensation process of water vapor. Our results show that an electric field can rotate water molecules upward and restrict condensation. Formed clusters are stretched to become columns above the threshold strength of the field, causing the condensation rate to drop quickly. The enhancement of surface attraction force boosts the rearrangement of water molecules adjacent to the surface and exaggerates the threshold value for shape transformation. In addition, the contact area between clusters and the surface increases with increasing amounts of surface attraction force, which raises the condensation efficiency. Thus, the condensation rate of water vapor on a surface under an electric field is determined by competition between intermolecular forces from the electric field and the surface.

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Electrical Breakdown Mechanism of Transformer Oil with Water Impurity: Molecular Dynamics Simulations and First-Principles Calculations

Crystals ◽

10.3390/cryst11020123 ◽

2021 ◽

Vol 11 (2) ◽

pp. 123

Author(s):

Bin Cao ◽

Ji-Wei Dong ◽

Ming-He Chi

Keyword(s):

Molecular Dynamics ◽

Thermal Diffusion ◽

First Principles ◽

Electrical Breakdown ◽

Transformer Oil ◽

Water Molecules ◽

Conducting Channel ◽

Breakdown Mechanism ◽

Water Impurity ◽

Dynamics Simulations

Water impurity is the essential factor of reducing the insulation performance of transformer oil, which directly determines the operating safety and life of a transformer. Molecular dynamics simulations and first-principles electronic-structure calculations are employed to study the diffusion behavior of water molecules and the electrical breakdown mechanism of transformer oil containing water impurities. The molecular dynamics of an oil-water micro-system model demonstrates that the increase of aging acid concentration will exponentially expedite thermal diffusion of water molecules. Density of states (DOS) for a local region model of transformer oil containing water molecules indicates that water molecules can introduce unoccupied localized electron-states with energy levels close to the conduction band minimum of transformer oil, which makes water molecules capable of capturing electrons and transforming them into water ions during thermal diffusion. Subsequently, under a high electric field, water ions collide and impact on oil molecules to break the molecular chain of transformer oil, engendering carbonized components that introduce a conduction electronic-band in the band-gap of oil molecules as a manifestation of forming a conductive region in transformer oil. The conduction channel composed of carbonized components will be eventually formed, connecting two electrodes, with the carbonized components developing rapidly under the impact of water ions, based on which a large number of electron carriers will be produced similar to “avalanche” discharge, leading to an electrical breakdown of transformer oil insulation. The water impurity in oil, as the key factor for forming the carbonized conducting channel, initiates the electric breakdown process of transformer oil, which is dominated by thermal diffusion of water molecules. The increase of aging acid concentration will significantly promote the thermal diffusion of water impurities and the formation of an initial conducting channel, accounting for the degradation in dielectric strength of insulating oil containing water impurities after long-term operation of the transformer.

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Origin and control of ionic hydration patterns in nanopores

Communications Materials ◽

10.1038/s43246-021-00162-x ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Miraslau L. Barabash ◽

William A. T. Gibby ◽

Carlo Guardiani ◽

Alex Smolyanitsky ◽

Dmitry G. Luchinsky ◽

...

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Distribution Functions ◽

Water Molecules ◽

Surrounding Water ◽

Ionic Hydration ◽

Hydration Shells ◽

Water Layers ◽

Dynamics Simulations ◽

And Control

AbstractIn order to permeate a nanopore, an ion must overcome a dehydration energy barrier caused by the redistribution of surrounding water molecules. The redistribution is inhomogeneous, anisotropic and strongly position-dependent, resulting in complex patterns that are routinely observed in molecular dynamics simulations. Here, we study the physical origin of these patterns and of how they can be predicted and controlled. We introduce an analytic model able to predict the patterns in a graphene nanopore in terms of experimentally accessible radial distribution functions, giving results that agree well with molecular dynamics simulations. The patterns are attributable to a complex interplay of ionic hydration shells with water layers adjacent to the graphene membrane and with the hydration cloud of the nanopore rim atoms, and we discuss ways of controlling them. Our findings pave the way to designing required transport properties into nanoionic devices by optimising the structure of the hydration patterns.

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