Atomistic QM/Classical Modeling of Surface-Enhanced Infrared Absorption.

Area of Science:

• Computational Chemistry
• Spectroscopy
• Materials Science

Background:

• Surface-enhanced infrared absorption (SEIRA) spectroscopy is crucial for studying molecular vibrations at surfaces.
• Accurate modeling of plasmon-molecule interactions is computationally demanding.
• Existing methods struggle to efficiently capture the complex interplay between molecules and plasmonic nanostructures.

Purpose of the Study:

• To introduce a novel multiscale quantum mechanics/molecular mechanics (QM/MM) approach for simulating SEIRA spectra.
• To enable accurate and computationally efficient modeling of molecules adsorbed on plasmonic nanostructures.
• To provide a robust framework for understanding plasmon-molecule hybrid systems.

Main Methods:

• The molecular subsystem is treated using density functional theory (DFT).
• The plasmonic material is modeled using frequency-dependent Fluctuating Charges (ωFQ) and Fluctuating Charges and Dipoles (ωFQFμ) models.
• The methodology is applied to adenine adsorbed on gold nanoparticles and graphene.

Main Results:

• The QM/MM approach accurately describes the plasmonic response of graphene and noble metal nanostructures.
• Simulated SEIRA spectra show good agreement with surface-enhanced Raman scattering (SERS) data and experimental results.
• The method achieves accuracy comparable to ab initio calculations with improved computational efficiency.

Conclusions:

• The proposed multiscale QM/MM framework offers a reliable and efficient method for simulating SEIRA spectra.
• This approach enhances the understanding of vibrational spectroscopy for plasmon-molecule hybrid systems.
• The methodology is applicable to various plasmonic materials and adsorbed molecules.