Web Release Date: December 4,
Optical Absorption Spectra and Polarizabilities of Silicon Carbide Nanotubes: A First Principles Study
and
Mesoscopic Physics Laboratory, Department of Physics, Peking University, Beijing 100871, P. R. China, and Department of Physics, University of Nebraska at Omaha, Omaha, Nebraska 68182-0266
Received: June 10, 2007
In Final Form: August 21, 2007
Abstract:
We have calculated the optical absorption spectra and polarizabilities of silicon carbide nanotubes by using
the density functional theory within the local density approximation. Most of the examined single-walled
silicon carbide nanotubes (SWSiCNTs) exhibit the first strong absorption peak around 3 eV, while the ultrathin
(5, 0) SWSiCNT exhibits the first three strong peaks in the 1.5-4.0 eV region. The screened polarizabilities
of SWSiCNTs are contributed by the localized valence electrons and can be described by a classical dielectric
cylindrical shell model, compared with the delocalized 
-electrons and the semimetallic shell model of carbon
nanotubes. The longitudinal screened polarizabilities of SWSiCNTs are apparently larger than the transverse
ones by a factor of 3.5-8.1, suggesting the possibility of their aligned synthesis in electric fields. In multiwalled
silicon carbide nanotubes, the inner tube is partially shielded by the outer tube for light polarized perpendicular
to the tube axis, compared with the nearly complete shielding effects in multiwalled carbon nanotubes.
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