Planar-to-tubular structural transition in boron clusters: B20 as the embryo of single-walled boron nanotubes
- Boggavarapu Kiran†,‡,§,
- Satya Bulusu§,¶,
- Hua-Jin Zhai†,‡,§,
- Soohaeng Yoo¶,
- Xiao Cheng Zeng¶,∥, and
- Lai-Sheng Wang†,∥
- †Department of Physics, Washington State University, 2710 University Drive, Richland, WA 99352; ‡Chemical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, MS K8-88, Richland, WA 99352; and ¶Department of Chemistry and Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588
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Edited by Ernest R. Davidson, University of Washington, Seattle, WA, and approved December 7, 2004 (received for review November 1, 2004)
Abstract
Experimental and computational simulations revealed that boron clusters, which favor planar (2D) structures up to 18 atoms,
prefer 3D structures beginning at 20 atoms. Using global optimization methods, we found that the B20 neutral cluster has a double-ring tubular structure with a diameter of 5.2 Å. For the 
anion, the tubular structure is shown to be isoenergetic to 2D structures, which were observed and confirmed by photoelectron
spectroscopy. The 2D-to-3D structural transition observed at B20, reminiscent of the ring-to-fullerene transition at C20 in carbon clusters, suggests it may be considered as the embryo of the thinnest single-walled boron nanotubes.
Footnotes
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↵ ∥ To whom correspondence may be addressed. E-mail: xczeng{at}phase1.unl.edu or ls.wang{at}pnl.gov.
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↵ § B.K., S.B., and H.-J.Z. contributed equally to this work.
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Author contributions: X.C.Z. and L.-S.W. designed research; H.-J.Z. performed experiments; B.K., S.B., and S.Y. performed calculations; and B.K., H.-J.Z., X.C.Z., and L.-S.W. wrote the paper.
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This paper was submitted directly (Track II) to the PNAS office.
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Abbreviations: PES, photoelectron spectroscopy; VDE, vertical detachment energy; HOMO, highest occupied molecular orbital; LUMO, lowest unoccupied molecular orbital; EA, electron affinity.
- Copyright © 2005, The National Academy of Sciences
