Using the MgO/Ag(100) interface as a model system, we demonstrate that Coul
omb and charge-transfer energies in oxide layers deposited on a highly pola
rizable medium like a metal, are reduced from their bulk values, by as much
as 1.8 eV and 2.5 eV, respectively. The use of efficient image potential s
creening may provide a new method to alter various transition temperatures
and properties of correlated oxides. [S0163-1829(99)51504-X].