The ionic cores are represented by projector augmented wave (PAW) potentials as constructed by Kresse and Joubert. The electronic one-particle wave functions are expanded in a plane-wave basis set up to a cutoff energy of 400 eV. This cutoff energy, which corresponds to the maximum cutoff for the four atomic species considered in this study (Pt, Ag, C, O) and is larger than the default values preset in the code for platinum and silver, was set manually in order to keep it constant for all calculations. Default cutoff energies are already expected to provide convergence better than 1 mRy (13 meV) in eigenvalues for this kind of basis set. Spin polarization is not considered due to the nonspin-polarized nature of the system. Dipole moment correction is set up in order to account for effects derived of using asymmetric slabs. Scalar relativistic effects are already included from the parametrization at the basis set generation. Convergence criteria for the electronic self-consistency and the ionic relaxation were set to 110 5 and 110 , respectively. A sufficiently large set of k-points was chosen in order to guarantee convergence.