Asymmetric bimetallic slabs comprised six atom layers, i.e., 24 atoms, which were separated by a vacuum layer of 24 Å. The two bottom layers of the host elements were fixed at their bulk positions, while the upper four layers were fully relaxed. The first Brillouin zone of the bimetallic slabs was integrated using a 6  6  1 k-point grid. The fully relaxed configurations were determined by the electronic energy convergence and the forces on ions with criteria of 110 -6 eV and 0.01 eV/Å, respectively. Finally, we would like to add that because of the similarity in these calculations, we expect relative energy changes by 0.01 eV to be significant.