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Calculating carbon nanotube–catalyst adhesion strengths
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory Group)
Tyndall National Institute.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. (Condensed Matter Theory Group)
Fysiska Institutionen, Göteborgs Universitet.
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2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 11, 115419- p.Article in journal (Refereed) Published
Abstract [en]

Density-functional theory is used to assess the validity of modeling metal clusters as single atoms or rings of atoms when determining adhesion strengths between clusters and single-walled carbon nanotubes (SWNTs). Representing a cluster by a single atom or ring gives the correct trends in SWNT-cluster adhesion strengths (Fe ≈ Co > Ni), but the single-atom model yields incorrect minimum-energy structures for all three metals. We have found that this is because of directional bonding between the SWNT end and the metal cluster, which is captured in the ring model but not by the single atom. Hence, pairwise potential models that do not describe directional bonding correctly, and which are commonly used to study these systems, are expected to give incorrect minimum-energy structures.

Place, publisher, year, edition, pages
2007. Vol. 75, no 11, 115419- p.
National Category
Physical Sciences
Research subject
Materials Science
URN: urn:nbn:se:uu:diva-108263DOI: 10.1103/PhysRevB.75.115419ISI: 000245329600124OAI: oai:DiVA.org:uu-108263DiVA: diva2:234802
Available from: 2009-09-10 Created: 2009-09-10 Last updated: 2012-03-14Bibliographically approved
In thesis
1. Computational Studies of Nanotube Growth, Nanoclusters and Cathode Materials for Batteries
Open this publication in new window or tab >>Computational Studies of Nanotube Growth, Nanoclusters and Cathode Materials for Batteries
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Density functional theory has been used to investigate cathode materials for rechargeable batteries, carbon nanotube interactions with catalyst particles and transition metal catalyzed hydrogen release in magnesium hydride nanoclusters.

An effort has been made to the understand structural and electrochemical properties of lithium iron silicate (Li2FeSiO4) and its manganese-doped analogue. Starting from the X-ray measurements, the crystal structure of Li2FeSiO4 was refined, and several metastable phases of partially delithiated Li2FeSiO4 were identified. There are signs that manganese doping leads to structural instability and that lithium extraction beyond 50% capacity only occurs at impractically high potentials in the new material.

The chemical interaction energies of single-walled carbon nanotubes and nanoclusters were calculated. It is found that the interaction needs to be strong enough to compete with the energy gained by detaching the nanotubes and forming closed ends with carbon caps. This represents a new criterion for determining catalyst metal suitability. The stability of isolated carbon nanotube fragments were also studied, and it is argued that chirality selection during growth is best achieved by exploiting the much wider energy span of open-ended carbon nanotube fragments.

Magnesium hydride nanoclusters were doped with transition metals Ti, V, Fe, and Ni. The resulting changes in hydrogen desorption energies from the surface were calculated, and the associated changes in the cluster structures reveal that the transition metals not only lower the desorption energy of hydrogen, but also seem to work as proposed in the gateway hypothesis of transition metal catalysis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 59 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 670
Materials science, density functional theory, cathode materials, hydrogen-storage materials, carbon nanotube growth
National Category
Other Physics Topics
Research subject
Physics of Matter; Materials Science
urn:nbn:se:uu:diva-108261 (URN)978-91-554-7603-8 (ISBN)
Public defence
2009-10-23, Polhemsalen, Ångströmlaboratoriet, Uppsala, 13:15 (English)
Available from: 2009-10-01 Created: 2009-09-10 Last updated: 2009-10-01

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Ahuja, Rajeev
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