First, the bulk energies (Eb) and bulk lattice parameters (db) of Pt and Ag were computed using an fcc unit cell and a 11  11  11 -centered k-point grid. Values obtained using PBE/PAW for the bulk lattice parameter are 3.97 Å and 4.15 Å for Pt and Ag, respectively. These are in close agreement with the experimental values of 3.9231 Å and 4.0862 Å. This yields nearest-neighbor distances of 𝑑 𝑠 = √2 2 𝑑 𝑏 of 2.81 Å and 2.93 Å for Pt(111) and Ag(111), respectively, which in the following we denote as surface lattice parameters. Using RPBE, the bulk lattice parameters for Pt and Ag are 3.99 Å and 4.21 Å respectively, and the nearest-neighbor distances for Pt(111) and Ag(111) are 2.82 Å and 2.98 Å, respectively. Note that RPBE yields a slightly larger overestimation of these parameters than PBE compared with the experimental values, as it is well known for many systems. The bimetallic surfaces are represented by periodic slabs consisting of five monolayers. The vertical height of the three-dimensional unit cell was set to an integer multiple of the surface lattice parameter, 10 ds, which allows us to have a separation between slabs close to 18 Å in all cases. Geometry optimization of the various surface configurations was carried out keeping the two bottom Pt(111) layers fixed at their corresponding bulk positions, while the three upper layers were allowed to relax.