In panel (a) of Figure , the sp!sp polarization energies are clearly similar across the metals Ag, Au, and Cu; but they are significantly lower for Pt and Rh, because it becomes easier to polarize Together, these findings offer further support to the d-band model. Overall, the variation in the adsorption energies of CH x on the metal surfaces, especially the polarization and charge transfer components, arise mainly from contributions from metal delectrons.