The structures, stabilities, and electronic properties of the single-vacancy-defected fullerenes, C-60 and C-70, and the single- and double-vacancy-defected single-walled carbon nanotubes (SWCNTs) were studied within density functional theory. The isomerization barriers for the single-vacancy-defected C,, on the triplet potential energy surface (PES) are lower than those on the singlet PES. The symmetric double-vacancy-defected (10,0) SWCNT is the most stable one among the models investigated. According to the analyses of frontier molecular orbitals (FMOs), nature bond orbitals, and local density of states, introduction of vacancy on the SWCNT decreases the band gap of semiconducting SWCNT, increases the band gap of conducting SWCNT, destructs the pi conjugation of the FMOs, and gives rise to enhanced chemical activity. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 109: 3441-3456, 2009

}, keywords = {BUCKMINSTERFULLERENE, C-60, COMPUTATIONS, CONDUCTANCE, density, EXCHANGE, FULLERENE, GENERALIZED GRADIENT APPROXIMATION, GROWTH, INHIBITION, OXIDES, single-walled carbon nanotube, vacancy defect}, isbn = {0020-7608}, url = {Single-walled carbon nanotubes (SWCNTs) have received significant attention from the scientific community over the past 15 years. Of particular interest is the potential of these macromolecules for use in molecular electronics, chemical sensory technology, nanobiology, and transition metal catalysis, For effective applications, the selective functionalization of the aforementioned all-carbon framework is necessary but has been met with considerable challenges. Herein, we review our approach to the exploration of structural and electronic properties of SWCNTs within density functional theory (DFT). Our investigations include mechanistic studies on chemical reactions of SWCNTs with defect and exploration of transition metal doped variants and their ability to adsorb small gas molecules.

}, keywords = {AB-INITIO, Defect, DOPED CARBON, ELECTRICAL-CONDUCTIVITY, ELECTROCHEMICALLY DEPOSITED FILMS, Electronic Structure, Gas Adsorption, GAUSSIAN-TYPE BASIS, GENERALIZED GRADIENT APPROXIMATION, LASER-ABLATION, MOLECULAR-ORBITAL METHODS, NANORODS, NITRIC-OXIDE, Nitrogen Monoxide, platinum, SIDEWALL FUNCTIONALIZATION, Single-Walled Carbon Nanotubes}, isbn = {1546-1955}, url = {Local density approximation (LDA), several popular general gradient approximation (GGA), hybrid module based density functional theoretical methods: SVWN, BLYP, PBE, HCTH, B3LYP, PBE1PBE, B1LYP, and BHandHLYP, and some nonstandard hybrid methods are applied in geometry prediction for C-60 and C-70. HCTH with 3-21G basis set is found to be one of the best methods for fullerene structural prediction. In the predictions of relative stability of C-50 isomers, PM3 is an efficient method in the first step for sorting out the most stable isomers. HCTH with 3-21G predicts very good geometries for C-50, similar to the performance of B3LYP/6-31G(d). The gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital from the predictions of all the density functional theory methods has the following descending order: E-gap(half-and-half hybrid)\> E-gap(B3LYP)\> E-gap(HCTH)(GGA)\> E-gap(SVWN)(LDA). (c) 2006 American Institute of Physics.

}, keywords = {ADJUSTABLE-PARAMETERS, BUCKMINSTERFULLERENE, C-70, DENSITY-FUNCTIONAL THEORY, ELECTRON-DIFFRACTION, ENERGIES, GENERALIZED GRADIENT APPROXIMATION, MOLECULAR-STRUCTURE, PERFORMANCE, PHASE, SEMIEMPIRICAL METHODS}, isbn = {0021-9606}, url = {