Center for Functional Nanomaterials Seminar

DFT has been used to calculate the electronic structure and 13C NMR chemical shifts of finite (9,0) and infinite (n,0) SWNTs with n ranging from 7 to 17. It is shown that direct comparison of the molecular and periodic approaches can be made if benzene is used as the internal (computational) reference. The results indicate that capping may have a strong effect on the computed properties. For the infinite systems, the shifts decrease roughly inversely proportional to the tube's diameter. 13C NMR has the potential for becoming a useful tool in characterizing SWNT samples.

The enhanced stability of so-called magic clusters is often explained by the formation of filled geometrical or electronic shells. Recent experiments on K - and Ba - C60 clusters have measured a set of magic peaks, which cannot be explained by either one of these mechanisms. We present DFT studies addressing the bonding and stability in Mn(C60)2clusters, with M= K, Ba and 1≤n≤6. The importance of calculating entropy in the determination of the most stable configuration is discussed.

A method that is able to generate truly minimal basis sets that accurately describe either a group of bands, a band or even just the occupied part of a band is outlined. These basis sets are the so-called NMTOs, muffin-tin orbitals of order N. The NMTOs are atom-centered and localized by construction, yielding Wannier functions for isolated bands. For bands that overlap others, Wannier-like functions may be generated. We show that NMTOs are able to give a chemical understanding of bonding within the solid state by applications to various systems.