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Neutral atoms in ionic lattices: Excited states of KCl:Ag(0)
Sousa Romero, Carmen; Graff, Cohen de; Illas i Riera, Francesc; Barriuso, M. T.; Aramburu, J. A.; Moreno Sereno, Mauricio
Universitat de Barcelona
The optical-absorption spectrum of a cationic Ag0 atom in a KCl crystal has been studied theoretically by means of a series of cluster models of increasing size. Excitation energies have been determined by means of a multiconfigurational self-consistent field procedure followed by a second-order perturbation correlation treatment. Moreover results obtained within the density-functional framework are also reported. The calculations confirm the assignment of bands I and IV to transitions of the Ag-5s electron into delocalized states with mainly K-4s,4p character. Bands II and III have been assigned to internal transitions on the Ag atom, which correspond to the atomic Ag-4d to Ag-5s transition. We also determine the lowest charge transfer (CT) excitation energy and confirm the assignment of band VI to such a transition. The study of the variation of the CT excitation energy with the Ag-Cl distance R gives additional support to a large displacement of the Cl ions due to the presence of the Ag0 impurity. Moreover, from the present results, it is predicted that on passing to NaCl:Ag0 the CT onset would be out of the optical range while the 5s-5p transition would undergo a redshift of 0.3 eV. These conclusions, which underline the different character of involved orbitals, are consistent with experimental findings. The existence of a CT transition in the optical range for an atom inside an ionic host is explained by a simple model, which also accounts for the differences with the more common 3d systems. The present study sheds also some light on the R dependence of the s2-sp transitions due to s2 ions like Tl+.
Espectres d'absorció
Excitació nuclear
Teoria del funcional de densitat
Química computacional
Propietats òptiques
Absorption spectra
Nuclear excitation
Density functional theory
Computational chemistry
Optical properties
(c) The American Physical Society, 2000
The American Physical Society

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