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Neutral atoms in ionic lattices: Study of KCl:Ag 0
Author(s) -
Cabria I.,
Barriuso M. T.,
Aramburu J. A.,
Moreno M.
Publication year - 1997
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1997)61:4<627::aid-qua3>3.0.co;2-y
Subject(s) - chemistry , ionic bonding , atom (system on chip) , transition metal , degenerate energy levels , electron paramagnetic resonance , charge (physics) , impurity , relaxation (psychology) , metal , electron , crystallography , atomic physics , ion , physics , nuclear magnetic resonance , quantum mechanics , organic chemistry , social psychology , psychology , biochemistry , computer science , embedded system , catalysis
To obtain better insight into the optical and EPR properties exhibited by the KCl:Ag 0 system, MS‐Xα and self‐consistent charge extended Hückel calculations as a function of the metal‐ligand distance, R , were carried out. As calculations on simple AgCl 6‐ 6 clusters led to inconsistent results (underlining that Ag 0 in KCl is a kind of shallow impurity), studies on (AgCl 6 K 12 Cl 8 ) 2‐ and (AgCl 6 K 12 Cl 8 K 6 Cl 24 K 24 ) 4+ were performed. The present results indicate that the stability of the Ag 0 center in KCl is related to a strong outward relaxation (of about 20%) of ligands, supporting previous analysis of the isotropic superhyperfine constant. Also, they explain the existence of one (and not two) charge‐transfer transitions in the V‐UV region, in spite of the zero nominal charge of the silver atom. As a curious feature, the e * g and t * 2g levels are practically degenerate and exhibit a pure 4 d character. This fact thus explains why the spin‐orbit splitting seen in the 4 d 10 5 s → 4 d 9 5 s 2 transitions is the same as in free Ag 0 . Although the a * 1g level coming from 5 s (Ag) is rather localized, it is shown that in the resonant t * 1u level [arising from 5 p (Ag)] the electron spends only 25% of its time on silver. This different behavior is related to the reduction of the 5 s → 5 p transition energy on passing from free atom to KCl:Ag 0 , which is in agreement with experimental findings. © 1997 John Wiley & Sons, Inc.