Density Functional Calculations of NMR Chemical Shifts in Carbon Nanotubes

Abstract

Computations of spectroscopic parameters of nanosystems can serve as an aid in experimental characterization. The focus of this article is on NMR (nuclear magnetic resonance) since in general this is one of the most versatile tools to study the structures, and properties of molecules and solids. After outlining the theory behind first–principles calculations of NMR parameters, it is illustrated that detailed information about the structure of carbon nanosystems can be obtained from these calculations. Theoretical studies of pristine SWNTs have indicated that 13C NMR may be used to determine the diameter distribution of a bulk sample. NICS (nucleus independent chemical shifts) have provided information about the aromaticity of various tubes, and the NMR chemical shifts of small molecules trapped in nanotubes have been calculated. Work on amine functionalized SWNTs has suggested that 13C NMR may be used to determine which nanotube carbons are derivatized, and perhaps even yield information about the diameter of the tubes. 13C NMR can potentially be useful to quantify the degree of fluorination. Theoretical studies on Stone-Wales defects have indicated that characteristic NMR signals may arise from atoms in the defect site. The tensor properties of nanotube NMR shielding is discussed.