Atomistic QM/Classical Modeling of Surface-Enhanced Infrared Absorption

TL;DR

This paper introduces a multiscale QM/MM approach combining DFT and atomistic plasmonic models to accurately simulate surface-enhanced infrared absorption spectra of molecules on nanostructures, validated against experimental data.

Contribution

The novel multiscale method integrates DFT with atomistic plasmonic models for efficient, accurate SEIRA spectra prediction of molecules on nanostructures.

Findings

Accurately reproduces SEIRA spectra of adenine on gold and graphene.

Achieves accuracy comparable to ab initio methods.

Provides a reliable simulation framework validated against experimental data.

Abstract

We present a multiscale quantum mechanics/classical (QM/MM) approach for modeling surface-enhanced infrared absorption (SEIRA) spectra of molecules adsorbed on plasmonic nanostructures. The molecular subsystem is described at the density functional theory (DFT) level, while the plasmonic material is represented using fully atomistic, frequency-dependent Fluctuating Charges ($\omega$FQ) and Fluctuating Charges and Dipoles ($\omega$FQF$\mu$) models. These schemes enable an accurate and computationally efficient description of the plasmonic response of both graphene-based materials and noble metal nanostructures, achieving accuracy comparable to ab initio methods. The proposed methodology is applied to the calculation of SEIRA spectra of adenine adsorbed on gold nanoparticles and graphene sheets. The quality and robustness of the approach are assessed through comparison with surface-enhanced Raman scattering (SERS) spectra and available experimental data. The results demonstrate that the proposed framework provides a reliable route to simulate vibrational responses of plasmon-molecule hybrid systems.