Atomic Adsorption on a Transition or d Metal

The density of states of a transition or d metal consists of a broad sp band and a narrow but intense d band, both of which are partly filled (see, for example. Fig. 6.17). In addition to the broadening and shifting of the adsorbate level, as in the case above, there is the strong interaction with the d band. In fact, the d band can be considered as a broad orbital itself, and its interaction with the adsorbate level leads 

The antibonding component will be occupied as far as it falls below the Fermi level of the metal, which weakens the adsorption bond somewhat. 

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