2017. 58, 1 UDC 541.6:547.12 CHEMICAL SHIELDING OF DOPED NITROGEN ON C20 CAGE AND BOWL FULLERENES F.R. Nikmaram1, A. Khoddamzadeh 2 2Young Researchers and Elite Club, Yadegar-e-Imam Khomeini (RAH) Branch, Islamic Azad University, Tehran, Iran Received June, 25, 2015 The C20 (cage), C20 (bowl), C20H10 (bowl) fullerene structures and their nitrogen doped derivatives such as C20NH (cage), C20NH (bowl), C20H10N (bowl), C20H10NH (bowl) are fully optimized at the MPW1PW91/6-31G level of theory. <...> The natural atomic charge comparison shows that in C20H10N (bowl), the nitrogen atom with about –0.58 has a more negative charge with respect to other nitrogen doped structures. <...> The nuclear magnetic resonance chemical shielding is evaluated for nitrogen doped structures and the neighbors connected to nitrogen, C6, and C7 atoms. <...> The nitrogen atom doped on carbon sites of C20H10N (bowl) has the largest shielding isotropic shifts to the upper field (–203.58 ppm). <...> This means that the electron density around nitrogen in the C20H10N (bowl) structure is higher. <...> Interestingly, there is a significant correlation between the charges and iso values of nitrogen and carbon atoms (C6 and C7). <...> Namely, as the charge becomes more negative, iso shifts to the upper field. <...> It is predicted that nitrogen doped C20H10N (bowl) with the maximum electron density adopts this structure for electrophilic reactions. <...> Among different carbon clusters, C20 is known as the smallest possible fullerene. <...> The experimental evidence of Prinzbach studies provided the existence of three different isomers of C20: cage, bowl, and ring [ 1, 2 ]. <...> Sokolovas studies on C20 by different quantum mechanical methods showed the different total energies of C20 isomers [ 4 ]. <...> The bowl isomer of C20 has the C5v symmetry with one central pentagon surrounded by five hexagons. <...> Based on DFT/LDA calculations, the cage isomer of C20 has a geometry with the lowest energy, while DFT with gradient corrected exchange correlation functions as well as Hartree—Fock calculations predict the ring geometry to be the most stable one [ 4, 7 ]. <...> According to the MP2/TZV2df calculation, the cage and bowl isomers of C20 are almost isoenergetic and more stable than the ring isomer <...>