Quadratic Jahn-Teller effect of fullerene anions

The quadratic Jahn-Teller effect of C-60(n-) (n = 1-5) is investigated from the first principles. Employing the density functional theory calculations with hybrid functional, the quadratic vibronic coupling constants of C-60(-) were derived. The warping of the adiabatic potential energy surface of C-60(-) by the quadratic vibronic coupling is estimated to be about 2 meV, which is much smaller than the Jahn-Teller stabilization energy (approximate to 50 meV). Because of the selection rule and the vibronic reduction, the quadratic coupling slightly modifies the vibronic states of C-60 anions. Particularly, in the case of C-60(3-), parity and symmetry selection rule significantly reduces the effect of quadratic coupling on vibronic states. The present results confirm that the low-energy vibronic dynamics of C-60(n-) is of pseudorotational type.