Structure of small silver clusters and static response to an external electric field

We present an extension of the charge-dipole model for the description of periodic systems. This periodic charge-dipole electrostatic model (PCDEM) allows one to describe the linear response of periodic structures in terms of charge- and dipole-type gaussian basis functions. The long-range electrostatic interaction is efficiently described by means of the continuous fast multipole method. As a first application, the PCDEM method is applied to describe the polarizability of silver slabs. We find that for a correct description of the polarizability of the slabs both charges and dipoles are required. However a continuum set of parametrizations, i.e., different values of the width of charge- and dipole-type gaussians, leads to an equivalent and accurate description of the slabs polarizability but a completely unphysical description of induced charge-density inside the slab. We introduced the integral squared density measure which allows one to obtain a unique parametrization which accurately describes both the polarizability and the induced density profile inside the slab. Finally the limits of the electrostatic approximations are also pointed out.

Section: Discussioncontrasting

confidence: 58%

A periodic charge-dipole electrostatic model: Parametrization for silver slabs

Bodrenko

Sierka

Fabiano

et al. 2012

“…The geometry optimization process was initiated from the structures found in the literature. 11,[40][41][42][43][44][45][46][47][48] New structures have also been tested, in particular, for n Ͼ 13, in which, to our knowledge, very few results are available. 47,48 The structures for a given size n were constructed from those obtained for smaller clusters with an additional Ag atom placed on different sites.…”

Section: Computationmentioning

confidence: 99%

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

Harb

Rabilloud

Simon

et al. 2008

220

305

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.

“…The ground-state structures of the bare silver clusters have been taken from our previous work on the static response of these clusters to an external electric field 21 and reoptimized with DEMON2K code 22 within the framework of an unrestricted Kohn-Sham quantum mechanics calculation. These structures are plotted in Fig.…”

Section: Method Structural and Computational Detailsmentioning

confidence: 99%

A first-principles study of the influence of helium atoms on the optical response of small silver clusters

Pereiro¹,

Baldomir²,

Arias³

2011

Self Cite

Optical excitation spectra of Ag(n) and Ag(n)@He(60) (n = 2, 8) clusters are investigated in the framework of the time-dependent density functional theory (TDDFT) within the linear response regime. We have performed the ab initio calculations for two different exact exchange functionals (GGA-exact and LDA-exact). The computed spectra of Ag(n)@He(60) clusters with the GGA-exact functional accounting for exchange-correlation effects are found to be generally in a relatively good agreement with the experiment. A strategy is proposed to obtain the ground-state structures of the Ag(n)@He(60) clusters and in the initial process of the geometry optimization, the He environment is simulated with buckyballs. A redshift of the silver clusters spectra is observed in the He environment with respect to the ones of bare silver clusters. This observation is discussed and explained in terms of a contraction of the Ag-He bonding length and a consequent confinement of the s valence electrons in silver clusters. Likewise, the Mie-Gans predictions combined with our TDDFT calculations also show that the dielectric effect produced by the He matrix is considerably less important in explaining the redshifting observed in the optical spectra of Ag(n)@He(60) clusters.