A Hybrid Density Functional Study of SiC Nanotubes

As a continuation of our previous work on SiC nanoclusters,$^{\ast }$ we report here first principles calculations on the electronic and geometric structures of armchair and zigzag silicon carbide nanotubes from (3,3) to (11,11) and (3,0) to (11,0) respectively. The finite cluster approach with dangling bonds terminated with hydrogen has been used. The theoretical formalism used is the hybrid density functional theory incorporating Hartree-Fock exchange with density functional theory exchange-correlation. In particular, we have used the B3LYP hybrid functional and the Los Alamos pseudopotential LANL2DZ$^{ }$as implemented in the Gaussian 03 suite of programs. For silicon, the 1s, 2s, and 2p electrons have been represented by core potentials and the remaining electrons as valence states. For carbon and hydrogen, all electron basis sets have been used. A detailed comparison of the structures and stabilities of the nanotubes has been performed. The dependence of the electronic band gaps on the respective tube diameters and energy density of states have also been investigated. Results will be compared with other published data in the literature where possible. $^{\ast }$ A. K. Ray and M. N. Huda, J. Comp. Th. Nanosci. \textbf{3}, 315 (2006).