The Influence of Gas-Wall and Gas-Gas Interactions on the Accommodation Coefficients for Rarefied Gases: A Molecular Dynamics Study.

Shahin Mohammad Nejad,David Smeulders,Arjan Frijns,Silvia Nedea

doi:10.3390/mi11030319

Shahin Mohammad Nejad, David Smeulders + Show 2 more

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https://doi.org/10.3390/mi11030319

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Journal: Micromachines	Publication Date: Mar 19, 2020
Citations: 13	License type: CC BY 4.0

Affiliation: Eindhoven University of Technology

Abstract

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.

Highlights

Rarefied gas condition is encountered in a broad range of modern engineering applications; for example, in low pressure devices such as semiconductor manufacturing and spacecraft flying at high altitudes, as well as small-scale structures such as microelectronic devices and micro/nanoelectromechanical systems (M/NEMS) [1,2]
Energy and momentum accommodation coefficients (E/MACs), which are the most relevant parameters involved in gas–surface interactions (GSI) models, describe the degree at which a gas attains its thermal or kinematic equilibrium with a surface while interacting with it
Molecular dynamics (MD) simulation is a very promising tool to determine different accommodation coefficients. These coefficients can be fed into semi-empirical GSI models such as Maxwell’s model [10] or Cercignani–Lampis–Lord (CLL) model [11] that can be employed as boundary conditions for higher-scale simulation techniques such as Direct Simulation Monte Carlo (DSMC) [12], Lattice Boltzmann method (LBM) [13], and method of moments (MoM) [14] to describe heat and mass flow at macroscopic level under rarefied condition

Summary

Introduction

Rarefied gas condition is encountered in a broad range of modern engineering applications; for example, in low pressure devices such as semiconductor manufacturing and spacecraft flying at high altitudes, as well as small-scale structures such as microelectronic devices and micro/nanoelectromechanical systems (M/NEMS) [1,2]. Energy and momentum accommodation coefficients (E/MACs), which are the most relevant parameters involved in GSI models, describe the degree at which a gas attains its thermal or kinematic equilibrium with a surface while interacting with it.

Results

Conclusion