Conditions for organized nanoring growth using kinetic Monte Carlo simulations

Dumont, F.; Picaud, Fabien; Ramseyer, Christophe; Giŗardet, C.

doi:10.1103/physrevb.77.153404

Cited by 6 publications

(7 citation statements)

References 36 publications

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“…Dumont et al (2008) have included the formation of ortho, para, meta, and 5 and S dimers (see Fig. 3, bottom panel) in their KMC calculations .…”

Section: H 2 Formation Using Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

“…The mechanisms included in our KMC simulations are the mechanisms M1 to M5 described in the introduction. Dumont et al (2008) have included in their KMC calculations formation of ortho, para, meta, and 5 and S dimers (see fig 3, right panel). The H atoms can diffuse from one dimer position to another.…”

Section: H 2 Formation Using Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

“…The others mechanisms included in their simulation contribute to the H 2 desorption but with a small amount. In this work we concentrate on H 2 formation on dust grains with temperatures smaller than 150 K. The mechanisms considered by Dumont et al (2008) are not relevant for the range of temperatures considered in this study since diffusion of chemisorbed H atoms as well as thermal recombinative desorption occur at much higher temperatures. In this study we use similar mechanisms as the ones considered in Cuppen & Hornekaer (2008), and also include the formation of H 2 with 2 physisorbed atoms.…”

Section: H 2 Formation Using Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

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When sticking influences H₂formation

Cazaux¹,

Morisset

Spaans³

et al. 2011

A&A

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Aims. Because of their catalytic properties, interstellar dust grains are crucial to the formation of H 2 , the most abundant molecule in the Universe. The formation of molecular hydrogen strongly depends on the ability of H atoms to stick on dust grains. In this study we determine the sticking coefficient of H atoms chemisorbed on graphitic surfaces, and estimate its impact on the formation of H 2 . Methods. The sticking probability of H atoms chemisorbed onto graphitic surfaces is obtained using a mixed classical-quantum dynamics method. In this, the H atom is treated quantum-mechanically and the vibrational modes of the surface are treated classically. The implications of sticking for the formation of H 2 are addressed by using kinetic Monte Carlo simulations that follow how atoms stick, move and associate with each other on dust surfaces of different temperature.Results. In our model, molecular hydrogen forms very efficiently for dust temperatures lower than 15 K through the involvement of physisorbed H atoms. At dust temperatures higher than 15 K and gas temperatures lower than 2000 K, H 2 formation differs strongly if the H atoms coming from the gas phase have to cross a square barrier (usually considered in previous studies) or a barrier obtained by density functional theory (DFT) calculations to become chemisorbed. The product of the sticking times efficiency can be increased by many orders of magnitude when realistic barriers are considered. If graphite phonons are taken into account in the dynamics calculations, then H atoms stick better on the surface at high energies, but the overall H 2 formation efficiency is only slightly affected. Our results suggest that H 2 formation can proceed efficiently in photon-dominated regions, X-ray dominated regions, hot cores and in the early Universe when the first dust is available.

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“…Dumont et al (2008) have included the formation of ortho, para, meta, and 5 and S dimers (see Fig. 3, bottom panel) in their KMC calculations .…”

Section: H 2 Formation Using Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

Section: H 2 Formation Using Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

Section: H 2 Formation Using Kinetic Monte Carlo Simulationsmentioning

confidence: 99%

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When sticking influences H₂formation

Cazaux¹,

Morisset

Spaans³

et al. 2011

A&A

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“…Finally Dumont et al [17] obtained H desorption from ortho-dimer configuration while in our model H desorption occurs almost exclusively from monomers and trimers.…”

Section: Comparison With Previous Workmentioning

confidence: 61%

“…Dumont et al [17] performed a similar study in which they simulated the TPD experiment by Zecho et al [6] using a Monte Carlo algorithm. Our explanation for the two TPD peaks agrees with theirs even if we used slightly different energy values, but there are also some differences.…”

Section: Comparison With Previous Workmentioning

confidence: 99%

A kinetic Monte Carlo study of desorption of H2 from graphite (0 0 0 1)

Gavardi

Cuppen

Hornekær

2009

Chemical Physics Letters

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The formation of H 2 in the interstellar medium proceeds on the surfaces of silicate or carbonaceous particles. To get a deeper insight of its formation on the latter substrate, this letter focuses on H 2 desorption from graphite (0001) in Temperature-Programmed-Desorption Monte-Carlo simulations. The results are compared to experimental results which show two main peaks and an intermediate shoulder for high initial coverage. The simulation program includes barriers obtained by ab-initio methods and is further optimised to match two independent experimental observations. The simulations reproduce the two experimental observed desorption peaks. Additionally, a possible origin of the intermediate peak is given.

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