Ensemble effects in adsorption - the interpolation principle

Such an estimate gives typical errors of the order 0.1 eV in the prediction of the chemisorption energy. A cruder model would be to use chemisorption energies 

however, its extreme simplicity means that the adsorption energy, on any alloy, can be estimated from a data base of adsorption energies calculated for the pure metals. In Table 4.2 we show such a data base [56]. 

While the interpolation model is far from perfect it gives a fast way of estimating the adsorption energies for alloys. Given the simplicity of the model it is surprising how well it works. The d band model can be used to indicate why this is the case. 

Under the assumption that AE0 in Eq. (5) is independent of the metal considered, all effects due to having several metal components, are to be found in the AEd term. We have seen above that Ed is a function of the d band center, and for small variations in ed, the relationship must be linear  

The d band center is given by the first moment of the chemisorption function, Eq. (10). We therefore need to understand qualitatively how ( ) behaves for a multi-component system. To see this it is useful to expand the metal wave functions 

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