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Optical spectroscopy of metallic icosahedral nanoparticles: classical versus atomistic description

AuthorsUrbieta, Mattin; Zhang, Yao; Barbry, Marc; Koval, P. CSIC ORCID; Sánchez-Portal, Daniel CSIC ORCID ; Zabala, Nerea CSIC ORCID; Aizpurua, Javier CSIC ORCID
Issue Date2016
CitationNanoSpain 2016
AbstractProgress in nanotechnology has allowed control of metallic nanoparticles at the nanometer and even subnanometer scale. Some of the most fascinating properties and applications of plasmonic nanoparticles are based on the tunability of their optical response and their ability to localize the electromagnetic fields around tips or at inter particle gaps. The near-fields are commonly addressed theoretically within classical frameworks. However, in some situations the atomic structure needs to be considered to correctly determine the response of the nanosystem. In this work we study the far- and near-field response of metallic nanoparticles and compare three different models. i) First, we use a classical modeling within a boundary element method (MNPBEM), which considers abrupt boundaries between media with homogeneous and isotropic dielectric functions to solve Maxwell's equations. Because the mean free path of the electrons is comparable to the size of the particles considered, the billiard model is used to approach surface scattering effects, with the resulting increase of damping in the dielectric function. ii) Secondly, we consider a discrete dipole approximation (DDA), in which each atom of the nanoparticle is described as a dipole and the atomistic structure is preserved. iii) Finally, our results are compared with atomistic ab-initio time-dependent density functional theory (TDDFT) calculations. We show that the general patterns of subnanometric localization and enhancement of fields can effectively be approached by classical means. The presence of tips and sharp endings in the geometry of the particle introduces a major enhancement and localization of the near-fields. Nevertheless, for the case of close particle dimers, differences arise due to the lack of quantum tunneling effects in the classical descriptions. In Figure 1) we show the near-field enhancement and the absorption cross section for a dimer of sodium icosahedral particles of radius 1.6 nm, as calculated in the classical BEM model.
DescriptionResumen del póster presentado a la NanoSpain Conference, celebrada en Logroño (España) del 15 al 18 de marzo de 2016.
Appears in Collections:(CFM) Comunicaciones congresos
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