The (compression corrected) interface energies, calculated via eqs. ( ) and ( ), are plotted as red bars in Fig. . For the AgPt system this is zero by definition. For the Ag film covered systems, we obtain slightly negative values. Hence, the interaction between the Pt and the laterally compressed, pseudomorphic Ag films is weakly attractive, slightly stronger than the mean Pt -Pt and Ag -Ag interactions. The positive character of the bulk formation energies is therefore dominated by the positive contribution from the Ag compression.