Silicon impacts on structure, stability and aromaticity of C20-nSin heterofullerenes (n = 1–10): A density functional perspective

Abstract

Density functional theory (DFT) calculations are applied to compare and contrast silicon atom substitution doped C20-nSin heterofullerene analogous with n = 1–10, at B3LYP/AUG-cc-pVTZ. Vibrational frequency analysis confirms that all studied systems are true minima. Isolating the dopants is an applicable strategy for obtaining highly doped stable heterofullerenes, since it avoids weak silicon―silicon single bonds. Comparing and contrasting the optimized geometries shows that except C11Si9 and C10Si10 species (with deformed cages of segregated analogous), all eight fullerenic cages are the complete isolated-pentagon analogous. Hence, the dopants must be completely isolated from each other by means of strong CC double bonds. Isolable or extractable fullerene isomers must be not only thermodynamically but also stable against electronic excitations. We then predicted that these isomers must have not only relatively large heats of atomization per carbon as a criterion of thermodynamic stability but also relatively large HOMO–LUMO energy separation against electronic excitations. The calculated the highest binding energy (6.52 eV/atom), heat of atomization per carbon (3193.2 kcal mol−1), band gap (2.86 eV) and nucleus independent chemical shift at the cage center (−50.00 ppm) for C18Si2 reveals it as the most stable heterofullerene. It has Ci symmetry and contains two silicon atoms in equatorial. High charge transfer on the surfaces of our scrutinized heterofullerenes provokes further investigations on their possible application for hydrogen storage. We hope that the present study will stimulate new experiments.