Quantum rotation of hydrogen in single-wall carbon nanotubes

Brown, Craig M.; Yildirim, Taner; Neumann, D. A.; Heben, Michael J.; Gennett, Thomas; Dillon, Anne C.; Alleman, J.; Fischer, J. E.

doi:10.1016/s0009-2614(00)01003-4

Cited by 132 publications

(82 citation statements)

References 25 publications

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“…9,10 The observed splitting is about 1 meV, suggesting the idea that in those experiments hydrogen molecules were probably not inside the nanotubes. The calculated para-to-ortho splitting of 3.2 meV is slightly larger than the 2.6 meV splitting observed for H 2 on graphite.…”

Section: A Para To Ortho Conversionmentioning

confidence: 74%

“…The study of quantum dynamics of hydrogen molecules in confined geometries has recently developed into an active field both experimentally and theoretically [1][2][3][4][5][6][7][8][9][10][11][12] due to potential use as catalysts, molecular sieves, and storage media. In the case of fullerenes and nanotubes, such trapping may yield new exotic quantum systems due to zero and one dimensionality of the absorption sites, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Several neutron and Raman scattering experiments have been carried out to characterize the binding energies and rotational barriers for H 2 at these sites with conflicting results. [1][2][3][4][9][10][11] One of the motivations of the present work is to provide a detailed description of the RV dynamics of H 2 molecules at these different absorption sites and discuss the consequences for inelastic neutron scattering experiments. In the present paper, we focus our attention on the general formalism and discuss only the case where a single H 2 is confined inside a single nanotube.…”

Section: Introductionmentioning

confidence: 99%

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Quantum dynamics of a hydrogen molecule confined in a cylindrical potential

Yildirim

Harris

2003

Phys. Rev. B

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We study the coupled rotation-vibration levels of a hydrogen molecule in a confining potential with cylindrical symmetry. We include the coupling between rotations and translations and show how this interaction is essential to obtain the correct degeneracies of the energy level scheme. We applied our formalism to study the dynamics of H 2 molecules inside a "smooth" carbon nanotube as a function of tube radius. The results are obtained both by numerical solution of the (2J+1)-component radial Schrödinger equation and by developing an effective Hamiltonian to describe the splitting of a manifold of states of fixed angular momentum J and number of phonons N. For nanotube radius smaller than ≈3.5Å, the confining potential has a parabolic shape and the results can be understood in terms of a simple toy model. For larger radius, the potential has the "Mexican hat" shape and therefore the H 2 molecule is off centered, yielding radial and tangential translational dynamics in addition to rotational dynamics of H 2 molecule which we also describe by a simple model. Finally, we make several predictions for the the neutron scattering observation of various transitions between these levels. Disciplines Physics | Quantum Physics CommentsAt the time of publication, author Taner Yildirim was affiliated with the National Institute of Standards and Technology, Gaithersburg, Maryland. Currently, he is a faculty member in the Materials Science and Engineering Department at the University of Pennsylvania.This journal article is available at ScholarlyCommons: http://repository.upenn.edu/physics_papers/336 We study the coupled rotation-vibration levels of a hydrogen molecule in a confining potential with cylindrical symmetry. We include the coupling between rotations and translations and show how this interaction is essential to obtain the correct degeneracies of the energy level scheme. We applied our formalism to study the dynamics of H 2 molecules inside a ''smooth'' carbon nanotube as a function of tube radius. The results are obtained both by numerical solution of the (2Jϩ1)-component radial Schrödinger equation and by developing an effective Hamiltonian to describe the splitting of a manifold of states of fixed angular momentum J and number of phonons N. For nanotube radius smaller than Ϸ3.5 Å, the confining potential has a parabolic shape and the results can be understood in terms of a simple toy model. For larger radius, the potential has the ''Mexican hat'' shape and therefore the H 2 molecule is off centered, yielding radial and tangential translational dynamics in addition to rotational dynamics of H 2 molecule which we also describe by a simple model. Finally, we make several predictions for the the neutron scattering observation of various transitions between these levels. Quantum dynamics of a hydrogen molecule confined in a cylindrical potential

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Section: A Para To Ortho Conversionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantum dynamics of a hydrogen molecule confined in a cylindrical potential

Yildirim

Harris

2003

Phys. Rev. B

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“…[27,28] This comparison will give an answer to where the hydrogen molecules are located in the SWNT sample.…”

Section: Discussion Ins Resultsmentioning

confidence: 99%

“…Inelastic neutron spectra in samples containing soot and 20 ± 30 wt % or 50 vol % of single-walled carbon nanotubes have been published before by Brown et al [27] and Ren et al, [28] respectively. These samples contained significant amounts (80 ± 70 wt % and 50 vol %, respectively) of amorphous and nanocrystalline carbon as well as metal nanoparticles.…”

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confidence: 93%

Hydrogen Adsorption in Carbon Nanostructures: Comparison of Nanotubes, Fibers, and Coals

Schimmel¹,

Kearley²,

Nijkamp³

et al. 2003

Chemistry A European J

182

107

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Single-walled carbon nanotubes (SWNT) were reported to have record high hydrogen storage capacities at room temperature, indicating an interaction between hydrogen and carbon matrix that is stronger than known before. Here we present a study of the interaction of hydrogen with activated charcoal, carbon nanofibers, and SWNT that disproves these earlier reports. The hydrogen storage capacity of these materials correlates with the surface area of the material, the activated charcoal having the largest. The SWNT appear to have a relatively low accessible surface area due to bundling of the tubes; the hydrogen does not enter the voids between the tubes in the bundles. Pressure ± temperature curves were used to estimate the interaction potential, which was found to be 580 AE 60 K. Hydrogen gas was adsorbed in amounts up to 2 wt % only at low temperatures. Molecular rotations observed with neutron scattering indicate that molecular hydrogen is present, and no significant difference was found between the hydrogen molecules adsorbed in the different investigated materials. Results from density functional calculations show molecular hydrogen bonding to an aromatic CÀC bond that is present in the materials investigated. The claims of high storage capacities of SWNT related to their characteristic morphology are unjustified.

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Activation of Molecular Hydrogen

Kubas

Heinekey

2010

Physical Inorganic Chemistry

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Quantum rotation of hydrogen in single-wall carbon nanotubes

Cited by 132 publications

References 25 publications

Quantum dynamics of a hydrogen molecule confined in a cylindrical potential

Quantum dynamics of a hydrogen molecule confined in a cylindrical potential

Hydrogen Adsorption in Carbon Nanostructures: Comparison of Nanotubes, Fibers, and Coals

Activation of Molecular Hydrogen

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