Optical Properties of Au Nanoclusters from TD-DFT Calculations

Abstract

A time-dependent density-functional-theory (TD-DFT) approach is employed to investigate theoretically the optical response of Au nanoclusters of size around N = 150 atoms as a function of: (a) the approximation used for the DFT exchange-correlation (xc-) functional, (b) the shape of the nanocluster. The results of the local-density-approximation (LDA) and the van Leeuwen-Baerends (LB94) xc-functionals are compared on a set of 4 structural motifs: octahedral (N = 146), cuboctahedral (N = 147), icosahedral (N = 147), and cubic (N = 172), representative of both crystalline and noncrystalline motifs commonly encountered in the study of metal nanoclusters. It is found that the position of the peak in the photoabsorption spectrum is weakly dependent on the shape of the cluster but is strictly related to its size and to the DFT xc-functional used in the calculations, with the finding that the predictions of the LB94 xc-functional compare better with the available experimental data on the absorption spectrum of Au particles in this size range with respect to those of the LDA xc-functional. The detailed shape of the cluster becomes apparent in the form of the absorption spectrum, which can be symmetric or asymmetric in two different forms.

Electron Production by Sensitizing Gold Nanoparticles Irradiated by Fast Ions

“…However, we note that this excitation involves not only the 6s electrons (as it happens in the case of the LSPR located at about 2.3 eV [72][73][74][75]) but also some fraction of the 5d electrons because of the strong overlap between the s and d states.…”

“…It was stated that this feature is caused by the collective excitation of 6s electrons in the gold atoms [72][73][74][75]. The corresponding electronic levels are located in the vicinity of the Fermi surface, so that these electrons delocalize over the whole nanoparticle.…”

A new time dependent density functional algorithm for large systems and plasmons in metal clusters

“…We have tested the performance of the new TDDFT algorithm implemented in this work, on a series of small but rather different systems ( 37 The goal is to achieve a firm assessment of the accuracy of the method on small systems as well as of an accurate choice of the density fitting set. Finally, the large metal clusters have been selected since they have been already treated by standard TDDFT and offer therefore a good chance to compare the performances of the new method and test its numerical economy.…”

Plasmonic hot carrier dynamics in solid-state and chemical systems for energy conversion

“…Theoretical calculations can capture this effect by solving the Schrödinger equation for electronic states in the actual geometry, and using Fermi's Golden rule with optical matrix elements between these states to calculate the transition rate induced by the plasmon. The level of detail in the electronic states vary from analytical free-electron solutions [48,63,65], jellium timedependent density functional theory (TD-DFT), which neglects atomic-scale structure in the nuclear potential and therefore details in the band structure but approximately accounts for electron-electron interactions [64], to TD-DFT calculations with full band-structure for small metal clusters [59]. The full calculations are currently feasible only for clusters with very few atoms (2-3 nm across), whereas the free electron and jellium TD-DFT calculations can be extended to ∼ 20 nm nanoparticles and they yield qualitatively similar results [64].…”

“…More importantly, such calculations are critical for describing all the mechanisms of plasmon decay and gauging their relative contributions. Such calculations are currently feasible for nanoparticles containing up to a few hundred atoms, that is, 1-2 nm in size, and can explicitly account for the effects of nanoparticle shape with specific facets and surface states on the optical response and carrier generation [58][59][60].…”