Modelling potential dependent surface-enhanced raman scattering: electric field and charged cluster dual model

Abstract

The computation of electrochemical systems is very challenging because of the many variables involved. Among them, the effect of the electrode potential is particularly complex to be introduced in atomistic models. In this work, we propose a model where the surface excess of charge has been modelled with the tetrahedral-like clusters [Ag19]+, [Ag20]0 and [Ag19]-. We then modulate the effect of other surface charges implicitly as an external electric field and correlated a calculated magnitude like the electric charge on the adsorbate with the electrode potential, a purely experimental one. This model is tested with the potential-dependent Surface-Enhanced Raman Scattering (SERS) of pyridine. Namely, we investigated the changes in the Raman shifts and relative intensities due to the potential, and evaluated the different contributions (electromagnetic, charge-transfer) to the SERS spectra. Our preliminary results nicely reproduce the experimental trends and reveal that enhancement factors up to 10 to the 7th are achieved when the charge-transfer state interact with the bright local excitations of the metal cluster.