Uptake effects of two electrons for relative stability and atomic structures of carbon cluster isomers of C₂₀: Ab initio methods

This study examined the effect of the uptake of one and two electrons on the atomic structure of three isomers of C₂₀ clusters, namely the ring, bowl (corannulene like), and cage (the smallest fullerene). Geometry optimizations were performed using the hybrid density functional (B3LYP) methods for neutral, singly and doubly charged C₂₀, C₂₀^-, and C₂₀^2-. These results show that the symmetry of the lowest energies for ring and bowl isomers were not changed, whereas the increasing order of energy for the cage (the smallest fullerene) isomers was changed from D_2h < C_2h ≤ C₂ of C₂₀ through C_i < C_2h < C₂ < D_2h of C₂₀- to C_i < C₂ < D_2h < C_2h of C₂₀^2-. The reduced symmetry isomers of the cage have comparative energy and the ground state symmetry of the neutral and single and double charged C20 decreased with increasing number of electrons taken up in the point of energetics. Interestingly, the difference in energy between the ground state and the next higher energy state of C₂₀^2- was 3.5kcal/mol, which is the largest energy gap of the neutral, single anion and double anion of the cage isomers examined.