The bulk lattice parameters (db) of Pt, Pd, and Ag were computed using an (1  1  1) fcc unit cell with a 24  24  24 k-point grid. The resulting bulk lattice parameters of Pt, Pd, and Ag are 3.96, 3.93, and 4.14 Å, respectively. The lattice parameters from the PBE calculations exceed the experimental values of 3.92, 3.89, and 4.09 Å by about 1 %. Symmetric mono-and bimetallic bulk systems were described by 12 atom layers in (111) orientation with a (2  2) lateral unit cell, i.e., the bulk unit cell consists of 48 atoms. As will be described in more detail in the section 3.1, this included two 6-layer subsystems with a Pt(111) or Pd(111) substrate and Ag containing layers in the top, which were arranged in a mirrored configuration. In each subsystem, two layers of the host elements (Pt or Pd) were fixed at their bulk positions. The guest element Ag atoms replaced the host atoms in the middle of the relaxed layers, forming a mirrored layer configuration along the c-direction. The configurations of the remaining eight layers were optimized together with the unit cell size in the c-direction. The compressed Ag layers with the lateral lattice constants of Pt and Pd were computed using 12 fully relaxed Ag layers with adjustable c-axis size.