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A theoretical study of atomic oxygen chemisorption on the Ni(100) and Ni(111) surfaces
Author(s) -
Siegbahn Per E. M.,
Wahlgren Ulf
Publication year - 1992
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.560420506
Subject(s) - chemisorption , cluster (spacecraft) , chemistry , atomic orbital , excited state , oxygen , nickel , covalent bond , atomic physics , electron , molecular orbital , crystallography , molecule , physics , adsorption , organic chemistry , quantum mechanics , computer science , programming language
Abstract Atomic oxygen chemisorption has been studied for the fourfold hollow site of the Ni(100) surface and for the threefold hollow site of the Ni(111) surface. To model the Ni(100) surface, 10 different clusters in the range Ni 5 to Ni 41 were used, and for the Ni(111) surface, 11 different clusters in the range Ni 13 to Ni 43 were used. A detailed analysis of the orbital occupations of the cluster with and without oxygen for the different clusters shows that there are three different possible bonding mechanisms. In two of these, the basic feature is that a 1 electrons of the cluster are kicked out by the oxygen 2 p z orbital and moved to holes in the 2 p x , y orbitals. A picture where the oxygen electrons fit into the electronic structure of the cluster is emphasized. The third mechanism, which is applicable for only one cluster, can be described as the formation of two covalent bonds of E symmetry. The final best estimate of the oxygen chemisorption energy for the Ni(100) surface is about 130 kcal/mol, and for the Ni(111) surface, about 115 kcal/mol. In particular for the Ni(111) surface, an excited oxygen state with radical character is identified, which might be a catalytically important species. The excitation energy to reach this state should be on the order of 10 kcal/mol for the Ni(111) surface.