We present quantum mechanics (QM)/frequency dependent
fluctuating
charge (QM/ωFQ) and fluctuating dipoles (QM/ωFQFμ)
multiscale approaches to model surface-enhanced Raman scattering spectra
of molecular systems adsorbed on plasmonic nanostructures. The methods
are based on a QM/classical partitioning of the system, where the
plasmonic substrate is treated by means of the atomistic electromagnetic
models ωFQ and ωFQFμ, which are able to describe
in a unique fashion and at the same level of accuracy the plasmonic
properties of noble metal nanostructures and graphene-based materials.
Such methods are based on classical physics, i.e. Drude conduction
theory, classical electrodynamics, and atomistic polarizability to
account for interband transitions, by also including an ad-hoc phenomenological
correction to describe quantum tunneling. QM/ωFQ and QM/ωFQFμ
are thus applied to selected test cases, for which computed results
are compared with available experiments, showing the robustness and
reliability of both approaches.