The present study was conducted using 5 adsorbates (C atom and CH x ; x = 1-4) placed at 3 sites (ontop, bridge, hollow) on 5 different fcc(100) transition metal surfaces (Ag, Au, Cu, Pt, Rh), giving 75 distinct complexes. For each complex, 4⇥4⇥4 periodic cells were prepared using the Atomic Simulation Environment (ASE) package as illustrated in Figure (a). The unit cells were separated by a vacuum of 20 Å in the z-direction, and the bottom two layers of each slab were held fixed. All periodic calculations were performed using the VASP 5.4.1 package, which uses a plane-wave basis and the projector augmented wave method. An energy cutoff of 400 eV was used for the plane-wave basis, and a 4⇥4⇥1 Monkhorst-Pack k-point mesh was applied for Brillouin zone sampling. Partial occupancies were determined using the first-order Methfessel-Paxton scheme with a smearing width of k B T = 0.2 eV, while the final energies were extrapolated back to an electronic temperature of k B T = 0.0 eV. The blocked-Davidson and RMM-DIIS algorithms were used for the electronic minimization, and a conjugate gradient algorithm was used for the geometry relaxation. A convergence criterion of 10 6 eV was used for the electronic update and 10 4 eV for the ionic update.