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PDF of thesis T15411 PDF of thesis T15411 - (19 M)
Title Multi-scale material growth and erosion in extreme environments / Andrew M. Bell.
Name Bell, Andrew M. .
Abstract This work sets out to develop a model to analyse surface growth during high energy deposition. This is important to applications such as hypersonics and thin-film growth. We considered Molecular Dynamics (MD), an atomistic model which captures key details but can only simulate small systems at short timescales due to computational cost. We also considered kinetic Monte Carlo (kMC), a mesoscale model lacking a lot of the fine detail but using a vastly reduced computational cost, allowing the analysis of larger systems over longer timeframes. The many-body Sutton-Chen potential was employed in preference to the Lennard-Jones (a simple pairwise potential) in the MD code, capturing electronic density effects and how they affect the surface atom interactions. How the average surface height and surface roughness was affected by high energy atomic impingement was analysed for a variety of systems. A kMC code was then created that made use of the MD statistics to recreate the surface growth patterns, while allowing for much larger and longer simulations. Using MD, the average surface height initially decreases before growing linearly. Meanwhile the surface roughness grows rapidly initially before increasing more slowly. Analysis of the effect of polar and azimuthal angles showed that the surface started eroding above a polar angle of 50°, and that using random or fixed azimuthal angles angle only affected the surface substantially at polar angles above 70°. Using kMC, a surface size of 56 by 28 lattice sites served well as a model system for the deposition of 2.5 monolayers while larger surfaces were required to avoid finite size effects during the deposition of 40 monolayers. We conclude that we have developed a model that can be used to simulate the evolution of a surface during high energy deposition, applicable to realistic sizes and timeframes.
Publication date 2019
Name Brown, Richard. degree supervisor.
Name Mulheran, Paul. degree supervisor.
Name Scanlon, Tom. degree supervisor.
Name University of Strathclyde. Department of Chemical & Process Engineering.
Thesis note Thesis PhD University of Strathclyde 2019 T15411
System Number 000005857

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