The general Born-Oppenheimer Hamiltonian of an adsorbate is expressed with reference to an AO basis by means of the second quantization technique, and the part representing the in situ adcomplex (admolecule possibly involving adsorption site atoms) is decomposed so as to show how contributions of different effects can be separated. A basic reference Hamiltonian of the adcomplex is defined, and the suggestion is made that it essentially represents a molecular system susceptible of treatment in terms of ordinary localized bonds. This suggestion is shown to be valid for one thing in the highly unsaturated surface complex FeCO (compared with Fe5CO), provided maximum-localization hybrids are used as elements of the AO basis. The example treated has also been used to show how two kinds of effects can be introduced and discussed: inductive effects, which appear to result from hybridization and from feedback compensations to charge shifts, and charge transfer between the adcomplex and the surface. The proposed local (''chemical'') description of an adcomplex appears to be an extremely useful tool for describing such complex adsorbates as those associated with Fischer-Tropsch catalysts. (C) 1994 John Wiley and Sons, Inc.
Chemical Effects and Surface-properties - the Nature of An Adsorbed Complex
PELUSO, Andrea
1994-01-01
Abstract
The general Born-Oppenheimer Hamiltonian of an adsorbate is expressed with reference to an AO basis by means of the second quantization technique, and the part representing the in situ adcomplex (admolecule possibly involving adsorption site atoms) is decomposed so as to show how contributions of different effects can be separated. A basic reference Hamiltonian of the adcomplex is defined, and the suggestion is made that it essentially represents a molecular system susceptible of treatment in terms of ordinary localized bonds. This suggestion is shown to be valid for one thing in the highly unsaturated surface complex FeCO (compared with Fe5CO), provided maximum-localization hybrids are used as elements of the AO basis. The example treated has also been used to show how two kinds of effects can be introduced and discussed: inductive effects, which appear to result from hybridization and from feedback compensations to charge shifts, and charge transfer between the adcomplex and the surface. The proposed local (''chemical'') description of an adcomplex appears to be an extremely useful tool for describing such complex adsorbates as those associated with Fischer-Tropsch catalysts. (C) 1994 John Wiley and Sons, Inc.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
