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Abstract: Theoretical investigations at the M05-2X DFT level employing the 6-31G(d), 6-31G(d,p), 6-31+G(d,p) and cc-pVDZ basis sets show that all nucleic acid bases (NABs), guanine, adenine, cytosine, thymine and uracil form stable stacking complexes with the zigzag (7,0) single-walled carbon nanotube (SWCNT). The values of the BSSE corrected interaction energy suggested that among the bases guanine forms the most stable complex. The other bases generate complexes of similar stability with the considered SWCNT that are less stable than the guanine-SWCNT dimer. [Copyright &y& Elsevier]

Abstract: Theoretical investigations were performed to study the structures and properties of different carbon nanoclusters. The computed properties were compared with those of the fullerene. The studied systems included carbon nano capsule, carbon nano bowl (one side closed tube), carbon nano disk and fullerene. The geometries of all species were optimized at the B3LYP level of theory using the 6-31G(d) basis set. Geometry of the silicon analog of fullerene (Si60) was also optimized at the same level of the theory. The HOMO–LUMO energy gap, ionization potential and electron affinity of studied clusters are reported and compared with those of the fullerene. It was found that the computed electronic properties are significantly influenced by the shape and size of different carbon nanoclusters. [Copyright &y& Elsevier]

Abstract: Interaction of C60 with nucleic acid base guanine was investigated at the DFT-B3LYP, MP2 and ONIOM(MP2:B3LYP) levels of theory using the 3-21G(d), 6-31G(d) and 6-31G(d,p) basis sets. It was found that C60 forms a stable complex with guanine through stacking interaction with binding energy of 8.1kcal/mol at the MP2/6-31G(d) level. The ONIOM(MP2/6-31G(d):B3LYP/6-31G(d)) approach was found to be the most cost-effective method for such investigation. Neither the B3LYP method nor MP2 level with smaller basis set such as 3-21G(d) are found suitable for such investigation. [Copyright &y& Elsevier]