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Energy gaps, electronic structures, and x-ray spectroscopies of finite semiconductor single-walled carbon nanotubes
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
Chinese Acad Sci, Inst High Energy Phys, Beijing.
KTH, School of Biotechnology (BIO), Theoretical Chemistry.ORCID iD: 0000-0003-0007-0394
2008 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, no 8, 084707-1-084707-8 p.Article in journal (Refereed) Published
Abstract [en]

We report hybrid density functional theory calculations for electronic structures of hydrogen-terminated finite single-walled carbon nanotubes (6,5) and (8,3) up to 100 nm in length. Gap states that are mainly arisen from the hydrogen-terminated edges have been found in (8,3) tubes, but their contributions to the density of states become invisible when the tube is longer than 10 nm. The electronic structures of (6,5) and (8,3) tubes are found to be converged around 20 nm. The calculated band-gap energies of 100 nm long nanotubes are in good agreement with experimental results. The valence band structures of (6,5), (8,3), as well as (5,5) tubes are also investigated by means of ultraviolet photoelectron spectra (UPS), x-ray emission spectroscopy (XES), and the resonant inelastic x-ray scattering (RIXS) spectra theoretically. The UPS, XES and RIXS spectra become converged already at 10 nm. The length-dependent oscillation behavior is found in the RIXS spectra of (5,5) tubes, indicating that the RIXS spectra may be used to determine the size and length of metallic nanotubes. Furthermore, the chiral dependence observed in the simulated RIXS spectra suggests that RIXS spectra could be a useful technique for the determination of chirality of carbon nanotubes.

Place, publisher, year, edition, pages
2008. Vol. 128, no 8, 084707-1-084707-8 p.
Keyword [en]
Electronic structure; Energy gap; Semiconductor materials; Ultraviolet photoelectron spectroscopy; Valence bands; X ray photoelectron spectroscopy; Gap states; Hydrogen-terminated edges; Metallic nanotubes; Valence band structures
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:kth:diva-14218DOI: 10.1063/1.2839294ISI: 000254047200046Scopus ID: 2-s2.0-40149088031OAI: oai:DiVA.org:kth-14218DiVA: diva2:331790
Note
QC 20100726Available from: 2010-07-26 Created: 2010-07-26 Last updated: 2017-12-12Bibliographically approved
In thesis
1. First Principles Studies of Carbon Based Molecular Materials
Open this publication in new window or tab >>First Principles Studies of Carbon Based Molecular Materials
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to investigate carbon based molecular materials at first principles levels. Special attention has been paid to simulations of X-ray spectroscopies, including near edge X-ray absorption fine structure (NEXAFS), X-ray photoelectron, and X-ray emission spectroscopy, which can provide detailed information about core, occupied and unoccupied molecular orbitals of the systems under investigation. Theoretical calculations have helped to assign fine spectral structures in high resolution NEXAFS spectra of five azabenzenes (pyridine, pyrazine, pyrimidine, pyridazine and s-triazine), and to identify different local chemical environments among them. With the help of NEXAFS, the characters of important chemical bonds that might be responsible for the unique magnetic properties of the tetracyanoethylene compound has been revealed. Calculations have demonstrated that X-ray spectroscopies are powerful tools for isomer identification and structure determination of fullerenes and endohedral metallofullerenes. A joint experimental and theoretical study on metallofullerene Gd@C82 has firmly determined its equilibrium structure, in which the gadolinium atom lies above the hexagon on the C2 axis. It is found that the gadolinium atom could oscillate around its equilibrium position and that its oscillation amplitude increases with increasing temperature.

In this thesis, several new computational schemes for large-scale systems have been proposed. Parallel implementation of a central insertion scheme (CIS) has been realized, which allows to effectively calculate electronic structures of very large systems, up to 150,000 electrons, at hybrid density functional theory levels. In comparison with traditional computational methods, CIS provides results with the same high accuracy but requires only a fraction of computational time. One of its applications is to calculate electronic structures of nanodiamond clusters varying from 0.76 nm (29 carbons) to 7.3 nm (20,959 carbons) in diameter, which enabled to resolve the long-standing debate about the validity of the quantum confinement model for nanodiamonds. Electronic structures and X-ray spectroscopies of a series of single-walled carbon nanotubes (SWCNTs) with different diameters and lengths have been calculated, which have made it possible to interpret the existing experimental results.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. x, 63 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2008:10
Keyword
first principles simulations, carbon based molecular materials, X-ray spectroscopies
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-4724 (URN)978-91-7178-963-1 (ISBN)
Public defence
2008-05-23, FB42, AlbaNova, Roslagstullsbaken 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100727Available from: 2008-05-06 Created: 2008-05-06 Last updated: 2010-07-27Bibliographically approved

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