Optical absorption of small silver clusters: Agn, (n=4–22)

Abstract

We present a joint theoretical and experimental investigation of the absorption spectra of silver clusters Ag n ͑4 Յ n Յ 22͒. The experimental spectra of clusters isolated in an Ar matrix are compared with the calculated ones in the framework of the time-dependent density functional theory. The analysis of the molecular transitions indicates that the s-electrons are responsible for the optical response of small clusters ͑n Յ 8͒ while the d-electrons play a crucial role in the optical excitations for larger n values.

Ultraviolet-visible absorption of small silver clusters in neon: Agn (n = 1–9)

“…1 and the experimental spectra reported in Harb's paper, 7 the present spectra are much better resolved. Although the overall absorption spectrum looks similar, small structures not visible precedently clearly appear.…”

“…Neon provides a weakly interacting medium, revealing numerous details as shown for selected sizes in Ag n /N e, 17 Cu n /N e, 18 and Au n /N e. 19 We present here a new series of absorption measurements on silver clusters (Ag n (n = 1-9)) deposited at 6 K in solid neon. The main features of these new data are similar to those obtained in other rare gas matrices, 4,5,7 however spectra show much better resolution and structures not present in previous measurements are clearly seen. We suggest that these measurements shall be taken as a benchmark for actual and future calculations on neutral silver clusters.…”

“…7,39 We find in argon an intense peak at 4.50 eV, which is not present or barely visible in neon. It was suggested 7 that it corresponds to symmetry forbidden transitions lifted by the interaction with the matrix. Its absence in the weakly perturbing neon matrix supports this idea.…”

“…7 On the theoretical side several studies within different approximations have calculated the equilibrium geometries and electronic properties of silver clusters taking explicitly into account the effect of the d electrons. The absorption spectra of Ag n (n = 2-8) in the UV-Visible range have been determined in the framework of the linear response equation-of-motion coupled cluster method [8][9][10] and more recently within the time dependent density functional theory (TD-DFT) approximation 7,[11][12][13][14][15][16] for clusters containing up to 120 atoms. The reasonably good agreement between the main features of the experimental and theoretical data allowed to assign the measured spectra to given isomers, 7, 12 however several differences are still present.…”

Validation of Methods for Computational Catalyst Design: Geometries, Structures, and Energies of Neutral and Charged Silver Clusters

“…The answers are important in the short term for guiding choices of functionals for applications and in the long term for designing better density functionals. A particularly noteworthy previous study of this question is the work on neutral Ag clusters by Chen et al; 30 among many interesting results, they found that of six exchange−correlation functionals studied, the TPSS and M06 exchange−correlation functionals agree best with CCSD-(T) wave function calculations for the relative energies of Ag 7 and Ag 8 .…”