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The kinetic Monte Carlo method as a way to solve the master equation for interstellar grain chemistry.

Cuppen HM, Karssemeijer LJ, Lamberts T - Chem. Rev. (2013)

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Affiliation: Theoretical Chemistry, Institute for Molecules and Materials, Radboud University Nijmegen , 6525 AJ Nijmegen, The Netherlands.

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number on the grain considered never exceeded five... The resulting the steady-state recombination efficiency24where NH is the number of arriving H atoms and NH2 is the number of formed H2 molecules adsorption... Fractions lower than 1 effectively decrease the flux of behavior of H2 from graphite, testing the KMC simulations by an exponential function and reaches steady state... Swapping results Rate equation results were compared with microscopic KMC results... reactions leading to species such as H2 and H2O are found to dominate; for higher temperatures (T = 30 K) oxygenation starts to take over, leading to the formation becomes even worse and lattice-based KMC simulations of these systems The adaptive kinetic Monte Carlo method is an on-the-fly, off-lattice, KMC method is sufficient confidence that all low-lying saddle points have been found.

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Diffusion barrier forchemisorbed H atoms on graphite as a functionof the energy difference between the initial and final configurations.The diffusion barriers between dimer and tetramer configurations followthe same linear dependences (eq 33). Figurereproduced with permission from ref (87). Copyright 2008 AIP Publishing LLC.
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fig8: Diffusion barrier forchemisorbed H atoms on graphite as a functionof the energy difference between the initial and final configurations.The diffusion barriers between dimer and tetramer configurations followthe same linear dependences (eq 33). Figurereproduced with permission from ref (87). Copyright 2008 AIP Publishing LLC.

Mentions: Expression 32 was introduced by Cuppen andHerbst78 to introduce hampered movementand desorption because of surface roughness. Equation 33 was later introduced based on a study of hydrogen atom diffusionon graphite87 (see Figure 8). Here the barrier for diffusion was found to be linearlydependent on the energy difference between the initial state and thefinal state. For H on graphite, the binding energy of an atom is affectedby the specific arrangement of other hydrogen atoms chemisorbed inits vicinity. The same dependence of Ediff and ΔE is found for dimer structures, wheretwo H atoms are involved, and for tetramer structures with four atoms.This very nice correlation is probably an effect of the isotropicnature of the system and is possibly due to the strong chemisorptioninteractions that are at play. For diffusion of physisorbed CO ona hexagonal water ice surface, no correlation was found as can beseen from the top panel of Figure 9. Againthe energy difference between the initial and the final state is plottedversus the diffusion barrier. These barriers are obtained in off-latticeKMC simulations83 and will be discussedin more detail in section 7. Even less correlationis found for diffusion on an amorphous water substrate (bottom panelof Figure 9 based on unpublished results).Checks for the validity of eq 32 for diffusionon interstellar ice show a similar lack of structure.


The kinetic Monte Carlo method as a way to solve the master equation for interstellar grain chemistry.

Cuppen HM, Karssemeijer LJ, Lamberts T - Chem. Rev. (2013)

Diffusion barrier forchemisorbed H atoms on graphite as a functionof the energy difference between the initial and final configurations.The diffusion barriers between dimer and tetramer configurations followthe same linear dependences (eq 33). Figurereproduced with permission from ref (87). Copyright 2008 AIP Publishing LLC.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3934372&req=5

fig8: Diffusion barrier forchemisorbed H atoms on graphite as a functionof the energy difference between the initial and final configurations.The diffusion barriers between dimer and tetramer configurations followthe same linear dependences (eq 33). Figurereproduced with permission from ref (87). Copyright 2008 AIP Publishing LLC.
Mentions: Expression 32 was introduced by Cuppen andHerbst78 to introduce hampered movementand desorption because of surface roughness. Equation 33 was later introduced based on a study of hydrogen atom diffusionon graphite87 (see Figure 8). Here the barrier for diffusion was found to be linearlydependent on the energy difference between the initial state and thefinal state. For H on graphite, the binding energy of an atom is affectedby the specific arrangement of other hydrogen atoms chemisorbed inits vicinity. The same dependence of Ediff and ΔE is found for dimer structures, wheretwo H atoms are involved, and for tetramer structures with four atoms.This very nice correlation is probably an effect of the isotropicnature of the system and is possibly due to the strong chemisorptioninteractions that are at play. For diffusion of physisorbed CO ona hexagonal water ice surface, no correlation was found as can beseen from the top panel of Figure 9. Againthe energy difference between the initial and the final state is plottedversus the diffusion barrier. These barriers are obtained in off-latticeKMC simulations83 and will be discussedin more detail in section 7. Even less correlationis found for diffusion on an amorphous water substrate (bottom panelof Figure 9 based on unpublished results).Checks for the validity of eq 32 for diffusionon interstellar ice show a similar lack of structure.

View Article: PubMed Central - PubMed

Affiliation: Theoretical Chemistry, Institute for Molecules and Materials, Radboud University Nijmegen , 6525 AJ Nijmegen, The Netherlands.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

number on the grain considered never exceeded five... The resulting the steady-state recombination efficiency24where NH is the number of arriving H atoms and NH2 is the number of formed H2 molecules adsorption... Fractions lower than 1 effectively decrease the flux of behavior of H2 from graphite, testing the KMC simulations by an exponential function and reaches steady state... Swapping results Rate equation results were compared with microscopic KMC results... reactions leading to species such as H2 and H2O are found to dominate; for higher temperatures (T = 30 K) oxygenation starts to take over, leading to the formation becomes even worse and lattice-based KMC simulations of these systems The adaptive kinetic Monte Carlo method is an on-the-fly, off-lattice, KMC method is sufficient confidence that all low-lying saddle points have been found.

No MeSH data available.


Related in: MedlinePlus