Structures and Energetics of Regioisomers of C60 Dimer and Trimers

Abstract

Ten different regioisomers of C60 trimers with intact cages were studied using the empirical tight-binding (TB) total energy calculation and the semiempirical PM3, AM1, and MNDO methods. We determined the stable atomic structure and energies of 10 (C60)3 regioisomers with ETBTEC, PM3, AM1, and MNDO calculations. The dimerization of C60 is exothermic according to the density-functional-based nonorthogonal tight-binding (DF-TB) method; the semiempirical PM3, AM1, and MNDO; and the ab initio 3-21G LDA and HF calculations, but it is endothermic in both the TB and the ab initio B3LYP6-31G*//4-21G B3LYP calculations. Therefore, according to the TB calculations, the most stable regioisomer of C60 trimers is equatorial. The energies of the trans-3(C2), trans-1(D2h), trans-2(C2), trans-4(Cs), cis-1 (C3ν), cis-2(Cs), cis-3(C2), cis-1(Cs), and cis-2(C3ν) regioisomers relative to the equatorial regioisomer are 13,19, 20, 30, 66, 99, 169, 215, and 673 meV, respectively.