J. Chem. Phys., 127, 104308, 2007

 DOI:10.1063/1.2768361

H. Zetergren, G. Sánchez, S. Díaz-Tendero, M. Alcamí, and F. Martín

Theoretical study of the stability of multiply charged C70 fullerenes.

We have calculated the electronic energies and optimum geometries of C70q+ and C68q+fullerenes (q=014) by means of density functional theory. The ionization energies for C70 and C68 fullerenes increase more or less linearly as functions of charge, consistent with the previously reported behavior for C60 and C58 [S. Díaz-Tendero et al., J. Chem. Phys.123, 184306 (2005)]. The dissociation energies corresponding to the C70q+ → C68q+C2C70q+C68(q1)++C2+C70q+→ C68(q2)+C++C+C70q+C68(q3)++C2++C+, and C70q+C68(q4)++C2++C2+ decay channels show that C70q+ (like C60q+) is thermodynamically unstable for q6. However, the slope of the dissociation energy as a function of charge for a given decay channel is different from that of C60q+fullerenes. On the basis of these results, we predict q=17 to be the highest charge state for which a fission barrier exists for C70q+.

J. Nanosci. Nanosci., 7, 1329, 2007

DOI:10.1166/jnn.2007.311.

M. Alcamí, G. Sánchez, S. Díaz-Tendero, Y. Wang and F. Martín

Structural patterns in fullerenes showing adjacent pentagons: C20 to C70.  

We have analyzed in detail the structure of the smallest fullerenes Cn (20 ≤ n ≤ 72) obtained in B3LYP/6-31G* calculations. All these systems, except for C60, C70, and C72, necessarily present adjacent pentagons in their structure. For the most stable classical isomers, we have studied the variation of bond distances, HOMO-LUMO gaps and enthalpies of formation with fullerene size. A classification of the bonds in 9 different motifs permits to gain insight in the factors determining the fullerene stability. A simplified model that assumes a fixed energy per bond is able to reproduce the calculated enthalpies of formation and to estimate the energy change associated with each structural motif. An extra stabilization of 30–40 kcal/mol is predicted for the fullerenes showing spherical aromaticity.

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