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Chemisorption of O and O 2 on Ag(110): An LCGTO ‐ LSD cluster study
Author(s) -
Selmani A.,
Andzelm J.,
Salahub D. R.
Publication year - 1986
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/qua.560290421
Subject(s) - chemistry , chemisorption , crystallography , cluster (spacecraft) , dissociation (chemistry) , ab initio , atomic orbital , molecular physics , atomic physics , computational chemistry , adsorption , physics , organic chemistry , quantum mechanics , computer science , programming language , electron
As part of a study aimed at better understanding of molecular and dissociative chemisorption of oxygen on Ag(110), linear combinations of Gaussian type orbitals‐local spin density ( LCGTO ‐ LSD ) calculations have been performed for O, O − , O 2 , O − 2 , O 2− 2 and a variety of silver clusters interacting with O or O 2 . For atomic O adsorption a very small cluster, Ag 4 , chosen to model the long‐bridge site already affords very good agreement with both recent EXAFS experiments and recent ab initio calculations. We calculate O to be 0.25 Å above the surface (exp. 0.2 Å). The Ag 4 O vibrational frequency is estimated to be 400 cm −1 , in reasonable accord with the experimental EELS value of 325 cm −1 . Determination of the geometry for O 2 (ads.) and, ultimately, of the dissociation path are far more difficult tasks. An extensive search for local minima in the vicinity of the LB site is being carried out. Results to date for small, Ag 2 and Ag 4 , clusters have furnished insight into the factors influencing the structure. Overlap between the π* orbital of the O 2 moiety and Ag s functions is a key factor; that is, there is an important covalent component of the binding. For geometries with O 2 parallel to the surface, this is achieved by twisting the O 2 fragment with respect to the [11¯0] grooves (geometries either parallel or perpendicular to the grooves yield zero π‖*− s overlap by symmetry). The structure with O 2 perpendicular to the surface also achieves reasonable overlap and lies close in energy to the most stable ‘parallel’ geometry.