  The structural optimization and energetics studies of SiC graphitic-like
structures have been investigated theoretically in the context of formations of
stable graphitic-like layer structures, single- and multi-walled nanotubes
using the DFT-based Vienna ab-inito simulation package. The bonding nature of
atoms in the optimized structures has been examined using a local analysis
technique based on a self-consistent and environment-dependent semi-empirical
Hamiltonian. Results of our studies reveal that stabilized SiC graphitic-like
layer structures possess the sp2 bonding nature, different from the sp3 bonding
nature in bulk SiC. Such flexibility in bonding configurations between Si and C
atoms holds the possibility for a wide range of stable SiC-based structures,
similar to those for carbon-based structures. In the case of SiC-based
nanotubes, we have calculated quantities such as the strain energy, the degree
of buckle in the cylindrical shell, and bond charges between Si and C atoms, to
obtain an understanding of the optimized structures. The optimized interlayer
spacing of SiC graphitic-like multilayer sheets has been found to depend on the
ordering of atoms in different layers of the SiC graphitic-like structure (0.37
nm for the Si-C sequence of bilayer arrangement versus 0.48 nm for either the
Si-Si or the C-C sequence of bilayer arrangement). These observations may be
attributed to the Coulomb interactions due to the charge redistribution among
Si and C atoms. On the other hand, the existence of two different ranges of
interlayer separation in SiC double-walled nanotubes (0.38 nm for zigzag and
0.48 nm for armchair) is found to be related to whether the dominant interlayer
neighbors are of the Si-C type or the Si-Si and C-C types.
