Theoretical investigations on stable structures of C60-nNn (n=2–12): Symmetry, model interaction, and global optimization

Abstract

Combining the extended cluster expansion method and the first-principles calculations, we have systematically investigated the structural stabilities of nitrogen doped C60 fullerene. With the structural recognition, we have calculated all possible isomers of C60-nNn (n = 1–4) to obtain their ground state structures using the first-principles method. For C60-nNn (n = 5–9) heterofullerenes, we have estimated the energy by the extended cluster expansion method to screen the candidates efficiently, followed by first-principles confirmation for the low-lying structures. For C60-nNn with more than 9 nitrogen atoms, we developed a classification method to select the candidates and successfully obtained the low-lying isomers. The most stable structures for C60-nNn (n = 3–11) we obtained have lower energies compared to the structures in previous studies. Notably, we have found 26 low-lying structures of C48N12 azafullerenes, from their 11.6 billion isomers.