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mmeineke |
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\subsection{RSA} |
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\label{sec:RSA_intro} |
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Random sequential adsorption, or RSA, describes the body of simulations where |
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a collection of sites or a continuum are sequetially and irreversibly |
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filled.\cite{evans1993} The RSA model has been used to simulate many types |
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of situations, from disociative chemisorption of $H_{2}O$ on an Fe (100) |
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surface,\cite{dwyer1977} to the arrangment of protiens on solid |
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surfaces.\cite{Macrichte1978}\cite{feder1980}\cite{ramsden1993} RSA can |
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provide a very powerful, yet simple model to simulate certain conditions. |
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One of the key components of RSA is the concept of irreversible filling of |
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the simulation space. Once the simulated entity lands on the surface, it is |
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considered to be immobile, nor will it desorb from the surface. There are |
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some models that allow for a certain window of movememnt when the entity |
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first adsorbs.\cite{dobson1987}\cite{egelhoff1989}\cite{evans1989} However, |
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at some point the entity is considered a fixed feature of the surface. |
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A distinct phenomenon that arrises out of RSA simulations, is the jamming |
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limit coverage, $\theta_{J}$. This coverage limit is closely dependent on the |
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shape of the entity, and is approached asymptotically as it becomes less |
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and less likely for an entity to find a place to land on the increasingly |
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crowded simulation space. $\theta_{J}$ for a 2D simulation of circles on |
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a plane, is 0.547,\cite{evans1993} and has been shown to decrease in systems |
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of increasingly anisotropic particles.\cite{viot1992} Although it is |
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interesting to note that the same paper also mentioned a slight increase in |
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coverage for entities only slightly removed from isotropy. |
