Atomistic Models for Plasmonics: from Metal Nanostructures to Molecular Plasmonics

This thesis introduces a family of classical atomistic electromagnetic multiscale models, referred to as ωMM, designed to simulate the optical properties of plasmonic materials with high accuracy and efficiency. Starting from the ωFQ model, originally developed for Drude-like plasmonic materials, the work extends this approach to noble metals by incorporating interband electron transitions. This enables the study of interactions between fully occupied and partially empty electronic states. The research further broadens the models' applicability to multimetallic systems, including bimetallic and alloyed nanostructures, by generalizing their mathematical formulation. Additionally, the ωMM framework has been reformulated to operate in the real-time domain, enabling the investigation of the time-dependent optical behavior of plasmonic materials. Another significant advancement is the development of models capable of simulating plasmonic interactions with non-absorbing and absorbing environments. These extensions facilitate the study of phenomena such as refractive-index-based localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS), making the framework applicable to sensors and nanophotonic devices.