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- Cutrarolo, Stefano, et al.
(författare)
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Thermodynamics of carbon in iron nanoparticles at low temperature : reduced solubility and size-induced nucleation of cementite
- 2010
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3892. ; 6, s. 16-26
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Tidskriftsartikel (refereegranskat)abstract
- In this manuscript we present the thermodynamics of iron-carbon nano particles at low temperature. By combining classical molecular dynamics simulations, ab initio calculations, finite temperature thermodynamics modeling, and the “size/pressure approximation”, we address carbon-induced fluidization, size-induced eutectic point shift, and reduced solubility at the nanoscale. The results are used to describe, as functions of particle size, three scenarios in the catalytic chemical vapor deposition growth of single single-walled carbon nanotubes, corresponding to steady state-, limitedand no-growth.
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- Duan, Haiming, et al.
(författare)
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Computational studies of small carbon and iron-carbon systems relevant to carbon nanotube growth
- 2008
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Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 8:11, s. 6170-6177
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory (DFT) calculations show that dimers and longer carbon strings are more stable than individual atoms on Fe(111) surfaces. It is therefore necessary to consider the formation of these species on the metal surfaces and their effect on the mechanism of single-walled nanotube (SWNT) growth. The good agreement between the trends (energies and structures) obtained using DFT and those based on the Brenner and AIREBO models indicate that these analytic models provide adequate descriptions of the supported carbon systems needed for valid molecular dynamics simulations of SWNT growth. In contrast, the AIREBO model provides a better description of the relative energies for isolated carbon species, and this model is preferred over the Brenner potential when simulating SWNT growth in the absence of metal particles. However, the PM3 semiempirical model appears to provide an even better description for these systems and, given sufficient computer resources, direct dynamics methods based on this model may be preferred.
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- Duan, Haiming, et al.
(författare)
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Initial growth of single-walled carbon nanotubes on supported iron clusters: a molecular dynamics study
- 2007
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Ingår i: EUROPEAN PHYSICAL JOURNAL D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 43:1-3, s. 185-188
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations were used to study the initial growth of single-walled carbon nanotubes (SWNTs) on a supported iron cluster (Fe-50). Statistical analysis shows that the growth direction of SWNTs becomes more perpendicular to the substrate over time due to the weak interaction between carbon nanotube and the substrate. The diameter of the nanotube also increases with the simulation time and approaches the size of the supported iron cluster.
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- Duan, Haiming, et al.
(författare)
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Size dependent melting mechanisms of iron nanoclusters
- 2007
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Ingår i: CHEMICAL PHYSICS. - : Elsevier BV. - 0301-0104 .- 1873-4421. ; 333:1, s. 57-62
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations were used to study the change in the mechanism of iron cluster melting with increasing cluster size. Melting of smaller clusters (e.g., Fe-55 and Fe-100) occurs over a large temperature interval where the phase of the cluster repeatedly oscillates between liquid and solid. In contrast, larger clusters (e.g., Fe-300) have sharper melting points with surface melting preceding bulk melting. The importance of the simulation time, the force field and the definition of cluster melting is also discussed.
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