Jahn-Teller distortions and excitation energies in C60(n+)

TL;DR

This paper systematically analyzes Jahn-Teller distortions and excitation energies in C60 ions with charges from 1+ to 9+, revealing significant non-adiabatic effects that influence the ground state energies and spin configurations.

Contribution

It provides a comprehensive classification of Jahn-Teller minima and computes excitation energies and quantum corrections for all relevant charge states of C60.

Findings

Jahn-Teller distortions vary with charge and spin.

Electronic excitation energies spread over about 1 eV.

Non-adiabatic corrections can invert ground state spin configurations.

Abstract

Based on previously computed parameters for the electron-phonon couplings and the Coulomb exchange, we compute and classify the static Jahn-Teller distortions, i.e. the minima of the lowest adiabatic potential energy surface, of C60(n+), for all values of charge 1 <= n <= 9 and spin. We compute the intra-band electronic excitation energies in the different optimal geometries in the sudden approximation, and find a spread of the electronic states of roughly 1 eV. We also obtain the leading vibronic quantum corrections to the ground-state energy, equal to zero-point energy lowering due to the softening of the phonons at the adiabatic Jahn-Teller minima: these non-adiabatic corrections are so large that for 4 <= n <= 6 states of different spin symmetry turn lower than the high-spin adiabatic ground state.