End-cap effects on vibrational structures of finite-length carbon nanotubes

Takashi Yumura, Daijirou Nozaki, Shunji Bandow, Kazunari Yoshizawa, Sumio Iijima

研究成果: Contribution to journalArticle査読

50 被引用数 (Scopus)

抄録

Vibrational structures of C60-related finite-length nanotubes, C40+20n and C42+18n (1 ≤ n ≤ 4), in which n is, respectively, the number of cyclic cis- and trans-polyene chains inserted between fullerene hemispheres, are analyzed from density functional theory (DFT) calculations. To illuminate the end-cap effects on their vibrational structures, the corresponding tubes terminated by H atoms C20nH 20 and C18nH18 (1 ≤ n ≤ 5) are also investigated. DFT calculations show a broad range of vibrational frequencies for the finite-size nanotubes: high-frequency modes (1100-1600 cm-1) containing oscillations along tangential directions (tangential modes), medium-frequency modes (700-850 cm-1) whose oscillations are located on the edges or end caps, and low-frequency modes (300-600 cm-1) involving oscillations along the radial directions (radial modes). Broadening of the calculated frequencies is due to the number of nodes in the standing waves of normal modes in the finite-size tubes. In the capped tubes, calculated vibrational frequencies are insensitive to the number of chains (n), whereas in the uncapped tubes, most vibrational frequencies change significantly with an increase in tube length. The discrepancy in the size dependency is reasonably understood by their C-C bonding networks; the capped tubes have similar bond-length alternation patterns within the polyene chains irrespective of n, whereas the uncapped tubes have various bond-deformation patterns. Thus, DFT calculations illuminate that the edge effects have strong impacts on the vibrational frequencies in the finite-size nanotubes.

本文言語英語
ページ(範囲)11769-11776
ページ数8
ジャーナルJournal of the American Chemical Society
127
33
DOI
出版ステータス出版済み - 8 24 2005

All Science Journal Classification (ASJC) codes

  • 触媒
  • 化学 (全般)
  • 生化学
  • コロイド化学および表面化学

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