Strong metal-support interactions electronic interaction theory

A massive electron transfer between the metal particles and the supports (or promoters) and the penetration of an electric field into the metal are thus not realistic ideas on the through-the-metal interaction. However, there is one mechanism for such an interaction which is well supported by the quantum theory of chemisorption when a covalent chemisorption bond is formed, it causes periodic variation (with the distance) in the chemisorption bond strength in its environment. At the nearest site a repulsion is felt, on the next-nearest an attraction, etc. [46a]. However, it is important to realize how strong this interaction is. A realistic estimate, based on observations of the field ion emission images, shows that these interactions are comparable in their strength to the physical (condensation) van der Waals forces [46b]. 

It is difficult to point to the basic reason why the average-potential model is not better applicable to metallic solutions. Shimoji60 believes that a Lennard-Jones 6-12 potential is not adequate for metals and that a Morse potential would give better results when incorporated in the same kind of model. On the other hand, it is possible that the main trouble is that metal solutions do not obey a theorem of corresponding states. More specifically, the interaction eAB(r) may not be expressible by the same function as for the pure components because the solute is so strongly modified by the solvent. This point of view is supported by considerations of the electronic models of metal solutions.46 The idea that the solvent strongly modifies the solute metal is reached also through a consideration of the quasi-chemical theory applied to dilute solutions. This is the topic that we consider next. 

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