Divacancies in carbon nanotubes and their influence on electron scattering

Structural, Vibrational and Electronic Properties of Defective Single-Walled Carbon Nanotubes Functionalised with Carboxyl Groups: Theoretical Studies

Covalent sidewall functionalisation of defective zigzag single-walled carbon nanotubes [SWCNTs(10,0)] with COOH groups is investigated by using DFT. Four types of point defects are considered: vacancy (V), divacancy [V₂ (5-8-5), V₂ (555-777)], adatom (AA) and Stone-Wales (SW). The energetic, structural, electronic and vibrational properties of these systems are analysed. Decreasing reactivity is observed in the following order: AA>V>V₂ (555-777)>V₂ (5-8-5)>SW. These studies also demonstrate that the position in which a carboxyl group is attached to a defective SWCNT is of primary importance. Saturation of two-coordinate carbon atoms in systems with the vacancy V-7 and with the adatom AA-1(2) is 3.5-4 times more energetically favourable than saturation of three-coordinate carbon atoms for all studied systems. Vibrational analysis for these two systems shows significant redshifts of the ν(CO) stretching vibration of 96 and 123 cm^-1 compared to that for carboxylated pristine systems. Detailed electronic-structure analysis of the most stable carboxylated systems is also presented.