First-Principles Studies of the Vibrational Stark Effect in C60

C60 has played a central role in molecular and organic electronics, where coupling between charge and vibrational degrees of freedom is of paramount importance. Recent surface-enhanced Raman scattering (SERS) studies of C60-Au junctions have reported significant shifts in vibrational mode frequencies with applied bias. Here we compute the magnitude of the vibrational Stark effect in gas-phase C60 and seek to understand and simulate the shifts in Raman mode frequencies observed in these electromigration junction-SERS experiments. Using density functional theory and a finite-difference approach, we calculate trends in the vibrational Stark effect for different modes of gas-phase C60, comparing directly to experiment and assessing the role of substrate-induced charging and external electric fields. This work supported by DOE and computational resources provided by NERSC.