Efficient Simulation of Surface-Enhanced Raman Scattering with a Simplified Damped Response Theory

Theoretical studies on enhancement mechanisms of surface-enhanced Raman scattering (SERS) are usually carried out with full quantum mechanical methods to capture the specific interactions between molecules and substrates. However, due to the computational costs of methods like time-dependent density functional theory (TDDFT), simplified model systems are commonly adopted. In the framework of TDDFT, the damped response theory is usually invoked to give a unified description of both on- and off-resonance Raman spectra based on the calculation of polarizability derivatives. However, the computational costs of full TDDFT allow for modeling SERS spectra only using small metal clusters. In this work, we demonstrate the implementation of an efficient method that simplifies the damped response calculations for the simulation of both on- and off-resonance SERS spectra. This simplified damped response method is named as TBAOResponse. We first compare the absorption spectra of a regular small system calculated with TBAOResponse and full TDDFT to benchmark the new method. Then, we demonstrate the efficiency and accuracy of the new method by comparing the on- and off-resonance SERS spectra calculated with different methods. Compared to full TDDFT, while significant improvement of efficiency is achieved, the simplified damped response maintains good accuracy for SERS calculation. We further showcase the efficiency of TBAOResponse by calculating the SERS spectra for a system that is computationally demanding with full TDDFT. This new method is promising for modeling SERS systems when a full quantum mechanical description of both the substrate and the molecule is necessary.