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Träfflista för sökning "hsv:(NATURVETENSKAP) hsv:(Kemi) hsv:(Materialkemi) ;pers:(Bolton Kim)"

Sökning: hsv:(NATURVETENSKAP) hsv:(Kemi) hsv:(Materialkemi) > Bolton Kim

  • Resultat 1-10 av 36
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1.
  • Börjesson, Anders, et al. (författare)
  • Modelling of Ostwald ripening of metal clusters attached to carbon nanotubes
  • 2011
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:50, s. 24454-24462
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a model of Ostwald ripening of nanosized clusters and apply it to study the time evolution of metal particles attached to carbon nanotubes. The Ostwald ripening of metal clusters attached to carbon nanotubes differs from that of free metal clusters. While free clusters experience a rapid broadening in the size dispersion, this may be delayed by the nanotubes, which may therefore limit the ripening. The diameter and chirality of the carbon nanotubes were also seen to affect the Ostwald ripening of the catalyst particles. For a collection of carbon nanotubes that contains different diameters and chiralities, the clusters attached to carbon nanotubes with large diameters and strong carbon–metal adhesion are the most likely to survive the Ostwald ripening.
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2.
  • Börjesson, Anders, et al. (författare)
  • Molecular modelling of oxygen and water permeation in polyethylene
  • 2013
  • Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 54:12, s. 2988-
  • Tidskriftsartikel (refereegranskat)abstract
    • Monte Carlo and molecular dynamics simulations were performed to calculate solubility, S, and diffusion, D, coefficients of oxygen and water in polyethylene, and to obtain a molecular-level understanding of the diffusion mechanism. The permeation coefficient, P, was calculated from the product of S and D. The AMBER force field, which yields the correct polymer densities under the conditions studied, was used for the simulations, and it was observed that the results were not sensitive to the inclusion of atomic charges in the force field. The simulated S for oxygen and water are higher and lower than experimental data, respectively. The calculated diffusion coefficients are in good agreement with experimental data. Possible reasons for the discrepancy in the simulated and experimental solubilities, which results in discrepancies in the permeation coefficients, are discussed. The diffusion of both penetrants occurs mainly by large amplitude, infrequent jumps of the molecules through the polymer matrix.
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3.
  • Bazooyar, Faranak, 1972, et al. (författare)
  • Validating empirical force fields for molecular-level simulation of cellulose dissolution
  • 2012
  • Ingår i: Computational and Theoretical Chemistry. - : Elsevier BV. - 2210-271X .- 2210-2728. ; 984, s. 119-127
  • Tidskriftsartikel (refereegranskat)abstract
    • The calculations presented here, which include dynamics simulations using molecular mechanics force fields and first principles studies, indicate that the COMPASS force field is preferred over the Dreiding and Universal force fields for studying dissolution of large cellulose structures. The validity of these force fields was assessed by comparing structures and energies of cellobiose, which is the shortest cellulose chain, obtained from the force fields with those obtained from MP2 and DFT methods. In agreement with the first principles methods, COMPASS is the only force field of the three studied here that favors the anti form of cellobiose in the vacuum. This force field was also used to compare changes in energies when hydrating cellobiose with 1-4 water molecules. Although the COMPASS force field does not yield the change from anti to syn minimum energy structure when hydrating with h more than two water molecules - as predicted by OFT - it does predict that the syn conformer is preferred when simulating cellobiose in bulk liquid water and at temperatures relevant to cellulose dissolution. This indicates that the COMPASS force field yields valid structures of cellulose under these conditions. Simulations based on the COMPASS force field show that, due to entropic effects, the syn form of cellobiose is energetically preferred at elevated temperature, both in vacuum and in bulk water. This is also in agreement with DFT calculations.
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5.
  • Bohlén, Martin, et al. (författare)
  • Computational Studies of Poly(vinylidene fluoride)-Single Wall Carbon Nanotube Systems
  • 2013
  • Ingår i: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 10:6, s. 1317-1325
  • Tidskriftsartikel (refereegranskat)abstract
    • First principles and molecular mechanics methods have been used to study poly(vinylidene fluoride)—single wall carbon nanotube systems. First principles calculations (Møller-Plesset second order perturbation theory and density functional theory with B3LYP exchange correlation functional with and without dispersion correction) using short poly(vinylidene fluoride) segments and short hydrogen-capped single wall carbon nanotubes show that the polymer segments prefer to have the β-rather than the β-conformation both in the absence and presence of the single wall carbon nanotube. The lowest energy structure is obtained when the poly(vinylidene fluoride) has an β-conformation and is located parallel to the single wall carbon nanotube wall. In contrast to the Dreiding and Universal force fields, the COMPASS force field predicts the structures containing the β-conformation of poly(vinylidene fluoride) to be the lowest in energy in agreement with first principles results. The COMPASS force field was consequently used in preliminary studies of a longer poly(vinylidene fluoride) chain and a longer single wall carbon nanotube using molecular dynamics.
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6.
  • Bolton, Kim, et al. (författare)
  • Computational Studies of Catalytic Particles for Carbon Nanotube Growth
  • 2009
  • Ingår i: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 6:1, s. 1-15
  • Tidskriftsartikel (refereegranskat)abstract
    • We review our computational studies of the melting temperatures and mechanisms of iron and iron-carbide clusters. Both isolated and supported clusters have been considered, and substrates with different shapes or pores have been simulated. It has been seen, for example, that the surface curvature—or local surface curvature—of the particle plays a dominant role in the melting mechanism and temperature. It has also been observed that the melting mechanism for small clusters is different to that of larger clusters.
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7.
  • Bolton, Kim, et al. (författare)
  • Computational studies of single-walled carbon nanotube growth
  • 2011
  • Ingår i: SNIC Progress Report (2008-2009). - : Swedish National Infrastructure for Computing. ; , s. 40-46
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Allocation of time on the Swedish national supercomputing facilities since 2000, as well as support from other sources, has allowed us to perform computational studies on a wide variety of systems. These include properties and growth of carbon nanotubes [1–36], icecatalysed reactions of importance to stratospheric ozone depletion[37], calculations of vapour-liquid, liquid-liquid and vapour-liquid-liquid phase equilibrium of single, binary and ternary component systems[38], and, more recently, carbonaceous polymer nanocomposites and cellulose decomposition. More details of these projects are available at the web page given above.
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9.
  • Bolton, Kim, et al. (författare)
  • Progress in understanding controlled single-wall carbon nanotube growth from computer simulations
  • 2012
  • Ingår i: Journal of Computational and Theoretical Nanoscience. - : American Scientific Publishers. - 1546-1955 .- 1546-1963. ; 9:6, s. 819-825
  • Tidskriftsartikel (refereegranskat)abstract
    • Density functional theory based on the PW91 and PBE exchange-correlation functionals was used to study processes that are expected to play a key role in single-walled carbon nanotube (SWNT) growth and continued growth. It is shown that Ni clusters adapt their shape to the shape of the SWNT end to which they are attached. The results also show that the presence of SWNTs affects Ostwald ripening of the catalyst metal clusters and that, under certain conditions, the net diffusion may be from larger to smaller clusters. Also, Ostwald ripening may affect the chiral distribution of the SWNTs.
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  • Resultat 1-10 av 36

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