Localized charge polarization by less-coordination: Rh adatoms, step edges, and added rows

he revolutionary impact of atomic under-coordination is indeed fascinating, which discriminates the processes of catalytic reaction and growth nucleation at defect sites from those at a flat surface, with mechanism that needs urgently to be known. A difference between the XPS Rh 3d5/2 spectra with and without artificial undercoordination reveals herewith excitingly that adatoms, step edge atoms, and atoms near the missing-row vacancies do induce localized polarization of the otherwise conductive s-electrons by the densely and tightly trapped core electrons; the extent of polarization is more significant for Rh atoms with even lower coordination numbers. The core electrons trapping happens because of the shorter and stronger local bonds and the associated quantum well depression.