Departamento de Física Aplicada, Universidade de Santiago de Compostela, Santiago de Compostela, Spain.
J Chem Phys. 2011 Feb 28;134(8):084307. doi: 10.1063/1.3556821.
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.
Ag(n) 和 Ag(n)@He(60)（n = 2,8）团簇的光激发谱在时间相关密度泛函理论（TDDFT）框架内进行了研究，处于线性响应区。我们对两种不同的完全交换泛函（GGA-精确和 LDA-精确）进行了从头算计算。对于具有 GGA-精确功能的 Ag(n)@He(60)团簇，计算出的光谱考虑了交换相关效应，通常与实验结果相对吻合较好。提出了一种获得 Ag(n)@He(60)团簇基态结构的策略，在初始的几何优化过程中，He 环境用富勒烯来模拟。与裸银团簇相比，He 环境中银团簇的光谱发生了红移。从 Ag-He 键长的收缩和银团簇中 s 价电子的限制两方面讨论并解释了这一观察结果。同样， Mie-Gans 预测结合我们的 TDDFT 计算也表明，He 基质产生的介电效应在解释 Ag(n)@He(60)团簇光学光谱中观察到的红移方面并不重要。
