Modeling plasmonic optical properties using semiempirical electronic structure calculations

This chapter focuses on the use of the semiempirical intermediate neglect of differential overlap Hamiltonian together with a configuration interaction (INDO/CI) treatment of optical excited states to study the optical properties of bare silver nanoclusters and silver nanoclusters with adsorbed pyridine molecules. It establishes a baseline comparison between INDO/CI and time-dependent density functional theory by studying small silver clusters such as tetrahedral Ag₂₀. To capture the effects of a plasmonic material on an adsorbed molecule, the chapter examines the cases of a tetrahedral Ag₂₀ cluster with a pyridine molecule adsorbed on either a vertex or a face of the tetrahedron in the absence of an applied potential. It also examines the effects of an applied potential on the surface-enhanced Raman spectroscopy spectra by utilizing the same orbital energy shift approximation that are used to study the charge-transfer states and the geometry dependence of the formal potential.