Binding energy coordination number dependence

This non-pairwise behaviour is most easily demonstrated by considering the coordination number dependence of the binding energy. It follows from eqs (5.68), (5.69), and (5.70) that the binding energy per atom of a lattice with coordination number may be written in the form... 

As we will discuss in more detail in Chapter 3, the delocalization of electrons is proportional to the square root of the number of coordinating atomsl l. One would therefore expect adsorbate binding energies to increase with decreasing particle size, owing to the increased number of coordinatively unsaturated surface atoms. The reactivity of these particles with respect to cluster size will then depend the position of the adsorbate bond energy with resp>ect to the Sabatier curve maximum. 

The other important parameter for the surface chemical bond is surface topology, i.e. the dependence of the surface bond energy of a surface adatom on the coordinative unsaturation of surface metal atoms. The changes in the adsorption properties of C on different Ru surfaces with different local coordination numbers have been studied in detail. A summary of the results is given in Table 3.3. Note that on the dense Ru(OOOl) surface atomic carbon prefers to bind to the three-fold coordination sites. 

---