Rapid growth of nanoscience and nanotechnology requires new and more powerful modeling tools. Efficient theoretical modeling of large molecular systems at the ab initio and Density Functional Theory (DFT) levels of theory depends critically on the size and completeness of the basis set used. The recently designed variants of STO-3G basis set (STO-3Gel, STO-3Gmag), modified to correctly predict electronic and magnetic properties were tested on simple models of pristine and functionalized carbon nanotube (CNT) systems and fullerenes using the B3LYP and VSXC density functionals. Predicted geometries, vibrational properties, and HOMO/LUMO gaps of the model systems, calculated with typical 6-31G* and modified STO-3G basis sets, were comparable. The (13)C nuclear isotropic shieldings, calculated with STO-3Gmag and Jensen's polarization consistent pcS-2 basis sets, were also identical. The STO-3Gmag basis sets, being half the size of the latter one, are promising alternative for studying (13)C nuclear magnetic shieldings in larger size CNTs and fullerenes.

A Chełkowski Institute of Physics University of Silesia 4 Uniwersytecka Street 40 007 Katowice Poland

Division of Statistics Department of Instrumental Analysis Medical University of Silesia 30 Ostrogórska Street 41 200 Sosnowiec Poland

Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences Flemingovo Nam 2 166 10 Prague Czech Republic

Institute of Physical Chemistry Polish Academy of Sciences 44 52 Kasprzaka Street 01 224 Warsaw Poland

Institute of Physics Polish Academy of Sciences 32 46 al Lotników 02 668 Warsaw Poland

Institute of Theoretical Physics and Astrophysics University of Gdańsk 57 Wita Stwosza Street 80 952 Gdańsk Poland

University of Opole Faculty of Chemistry 48 Oleska Street 45 052 Opole Poland

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