scholarly journals The Influence of Gas–Wall and Gas–Gas Interactions on the Accommodation Coefficients for Rarefied Gases: A Molecular Dynamics Study

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 319 ◽  
Author(s):  
Shahin Mohammad Nejad ◽  
Silvia Nedea ◽  
Arjan Frijns ◽  
David Smeulders
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Rarefied Gas ◽  
Interaction Strength ◽  
Gold Surface ◽  
Md Simulations ◽  
Accommodation Coefficients ◽  
Experimental Values ◽  
Energy And Momentum ◽  
Gas Interactions

Molecular dynamics (MD) simulations are conducted to determine energy and momentum accommodation coefficients at the interface between rarefied gas and solid walls. The MD simulation setup consists of two parallel walls, and of inert gas confined between them. Different mixing rules, as well as existing ab-initio computations combined with interatomic Lennard-Jones potentials were employed in MD simulations to investigate the corresponding effects of gas-surface interaction strength on accommodation coefficients for Argon and Helium gases on a gold surface. Comparing the obtained MD results for accommodation coefficients with empirical and numerical values in the literature revealed that the interaction potential based on ab-initio calculations is the most reliable one for computing accommodation coefficients. Finally, it is shown that gas–gas interactions in the two parallel walls approach led to an enhancement in computed accommodation coefficients compared to the molecular beam approach. The values for the two parallel walls approach are also closer to the experimental values.

Establishing a data-based scattering kernel model for gas–solid interaction by molecular dynamics simulation

2021 ◽  
Vol 928 ◽  
Author(s):  
Zijing Wang ◽  
Chengqian Song ◽  
Fenghua Qin ◽  
Xisheng Luo
Keyword(s):  
Machine Learning ◽  
Molecular Dynamics ◽  
Md Simulation ◽  
Rarefied Gas ◽  
Interaction Model ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Rarefied Gas Flows ◽  
Accommodation Coefficients ◽  
Scattering Kernel

Scattering kernel models for gas–solid interaction are crucial for rarefied gas flows and microscale flows. However, most existing models depend on certain accommodation coefficients (ACs). We propose here to construct a data-based model using molecular dynamics (MD) simulation and machine learning. The gas–solid interaction is first modelled by 100 000 MD simulations of a single gas molecule reflecting on the wall surface, which is fulfilled by GPU parallel technology. The results showed a correlation of the reflection velocity with the incidence velocity in the same direction, and also revealed correlations that may exist in different directions, which are neglected by the traditional gas–solid interaction model. Inspired by the sophisticated Cercignani–Lampis–Lord (CLL) model, two improved scattering kernels were constructed to better reproduce the probability density of velocity determined from MD simulation. The first one adopts variable ACs which depend on the incidence velocity and the second one combines three CLL-like kernels. All the parameters in the improved kernels are automatically chosen by the machine learning method. Compared with the numerical experiments of a molecular beam, the reconstructed scattering kernels are basically consistent with the MD results.

scholarly journals Unveiling Carbon Dioxide and Ethanol Diffusion in Carbonated Water-Ethanol Mixtures by Molecular Dynamics Simulations

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1711
Author(s):  
Mohamed Ahmed Khaireh ◽  
Marie Angot ◽  
Clara Cilindre ◽  
Gérard Liger-Belair ◽  
David A. Bonhommeau
Keyword(s):  
Carbon Dioxide ◽  
Molecular Dynamics ◽  
Diffusion Coefficients ◽  
Hydrodynamic Radius ◽  
Md Simulations ◽  
Molecular Models ◽  
Experimental Values ◽  
Carbon Dioxide Co2 ◽  
Dynamics Simulations ◽  
Apparent Disagreement

The diffusion of carbon dioxide (CO2) and ethanol (EtOH) is a fundamental transport process behind the formation and growth of CO2 bubbles in sparkling beverages and the release of organoleptic compounds at the liquid free surface. In the present study, CO2 and EtOH diffusion coefficients are computed from molecular dynamics (MD) simulations and compared with experimental values derived from the Stokes-Einstein (SE) relation on the basis of viscometry experiments and hydrodynamic radii deduced from former nuclear magnetic resonance (NMR) measurements. These diffusion coefficients steadily increase with temperature and decrease as the concentration of ethanol rises. The agreement between theory and experiment is suitable for CO2. Theoretical EtOH diffusion coefficients tend to overestimate slightly experimental values, although the agreement can be improved by changing the hydrodynamic radius used to evaluate experimental diffusion coefficients. This apparent disagreement should not rely on limitations of the MD simulations nor on the approximations made to evaluate theoretical diffusion coefficients. Improvement of the molecular models, as well as additional NMR measurements on sparkling beverages at several temperatures and ethanol concentrations, would help solve this issue.

Geometry of OH⋯O interactions in the liquid state of linear alcohols from ab initio molecular dynamics simulations

2020 ◽  
Vol 22 (12) ◽  
pp. 6690-6697 ◽  
Author(s):  
Aman Jindal ◽  
Sukumaran Vasudevan
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonding ◽  
Ab Initio ◽  
Molecular Dynamics Simulations ◽  
Liquid State ◽  
Crystalline State ◽  
Md Simulations ◽  
Ab Initio Molecular Dynamics ◽  
Linear Alcohols ◽  
Dynamics Simulations

Hydrogen bonding OH···O geometries in the liquid state of linear alcohols, derived from ab initio MD simulations, show no change from methanol to pentanol, in contrast to that observed in their crystalline state.

scholarly journals Polydopamine and eumelanin molecular structures investigated with ab initio calculations

2017 ◽  
Vol 8 (2) ◽  
pp. 1631-1641 ◽  
Author(s):  
Chun-Teh Chen ◽  
Francisco J. Martin-Martinez ◽  
Gang Seob Jung ◽  
Markus J. Buehler
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Dft Calculations ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Density Functional ◽  
Md Simulations ◽  
Molecular Structures ◽  
Brute Force ◽  
Functional Theory

A set of computational methods that contains a brute-force algorithmic generation of chemical isomers, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations is reported and applied to investigate nearly 3000 probable molecular structures of polydopamine (PDA) and eumelanin.

Force field development and simulations of senior dialkyl sulfoxides

2016 ◽  
Vol 18 (15) ◽  
pp. 10507-10515 ◽  
Author(s):  
Vitaly V. Chaban
Keyword(s):  
Molecular Dynamics ◽  
Force Field ◽  
Ab Initio ◽  
Md Simulations ◽  
Field Development ◽  
Force Field Development ◽  
Structure And Dynamics ◽  
Ethyl Methyl ◽  
Methyl Sulfoxide ◽  
Diethyl Sulfoxide

Thermodynamics, structure, and dynamics of diethyl sulfoxide (DESO) and ethyl methyl sulfoxide (EMSO) were investigated using ab initio calculations and non-polarizable potential based molecular dynamics (MD) simulations.

Heat Transfer Predictions Using Accommodation Coefficients for a Dense Gas in a Micro/Nano-Channel

2008 ◽  
Author(s):  
S. V. Nedea ◽  
A. J. Markvoort ◽  
P. Spijker ◽  
A. A. van Steenhoven
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Md Simulations ◽  
Heat Fluxes ◽  
Dense Gas ◽  
Nano Channel ◽  
Accommodation Coefficients ◽  
Gas Interactions ◽  
Wall Interactions ◽  
Good Agreement

The influence of gas-gas and gas-wall interactions on the heat flux predictions for a dense gas confined between two parallel walls of a micro/nano-channel is realized using combined Monte Carlo (MC) and Molecular Dynamics (MD) techniques. The accommodation coefficients are computed from explicit MD simulations. These MD coefficients are then used as effective accommodation coefficients in Maxwell-like boundary conditions in MC simulations. We find that heat flux predictions from MC based on these coefficients compare good with the results of explicit simulations except the case when there are hydrophobic gas-wall/gas-gas interactions. For this case an artificial wall was introduced in order to measure these MD accommodation coefficients at this artificial border. Good agreement is found then for both hydrophilic and hydrophobic gas-wall interactions and we show this by confronting the heat fluxes from explicit MD simulations with the the MC heat flux predictions for all the generic accommodation coefficients.

Energetics and diffusion of liquid water and hydrated ions through nanopores in graphene: ab initio molecular dynamics simulation

2017 ◽  
Vol 19 (31) ◽  
pp. 20551-20558 ◽  
Author(s):  
Raúl Guerrero-Avilés ◽  
Walter Orellana
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Ab Initio Molecular Dynamics ◽  
Functional Theory ◽  
Hydrated Ions ◽  
And Diffusion

The energetics and diffusion of water molecules and hydrated ions (Na+, Cl−) passing through nanopores in graphene are addressed by dispersion-corrected density functional theory calculations and ab initio molecular dynamics (MD) simulations.

Physical properties of high-temperature solid alkali chlorides by molecular dynamics simulation using a recent EIM interatomic potential

2019 ◽  
Vol 33 (10) ◽  
pp. 1950088 ◽  
Author(s):  
Xiandai Cui ◽  
Jiaoqun Zhu ◽  
Hong Xu ◽  
Xiaomin Cheng ◽  
Weibing Zhou
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Interatomic Potential ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Experimental Values ◽  
Alkali Chlorides ◽  
Change Material

Thermophysical properties of phase change material NaCl and KCl were calculated using molecular dynamics (MD) simulations and a recent EIM interatomic potential. Density, thermal expansion coefficient, specific heat capacity were computed using equilibrium MD (EMD) simulations. The results are very close to the experimental values. The thermal conductivity was computed using two non-equilibrium MD (NEMD) methods and the results were compared with the experimental data. They appear to be relatively reasonable. Binary NaCl/KCl systems have also been investigated. The specific heat capacity with different compositions are calculated. They are very close with recent experimental results.

Investigation of Mechanical Properties of Epoxy EPON 862 Cured With TETA by Molecular Dynamics

2015 ◽  
Vol 4 (2) ◽  
Author(s):  
Ashwini Kumar Rai ◽  
Amit Porwal ◽  
S. B. Mishra
Keyword(s):  
Molecular Dynamics ◽  
Epoxy Resin ◽  
Material Properties ◽  
Linear Thermal Expansion ◽  
Md Simulations ◽  
Amorphous Structure ◽  
Thermal Expansion Coefficients ◽  
The Cross ◽  
Predicted Values ◽  
Experimental Values

Molecular dynamics (MD) simulations were conducted to estimate the material properties of the cross-linked epoxy resin compound. A periodic amorphous structure of the cross-linked epoxy resin compound was constructed and it was simulated by continuous accumulation of structure configurations at various temperatures. Based on the simulation results, glass transition temperature (Tg), linear thermal expansion coefficients and Young's modulus of the cross-linked epoxy resin compound were predicted. The predicted values of these material properties are in good agreement with the experimental values in the literature.

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