DFT calculations were performed using the Vienna ab initio simulation package (VASP). Electronic cores were represented with projector-augmented wave pseudopotentials. was used to interface with VASP. Exchange-correlation was treated with the RPBE functional 55 with Grimme's D3 dispersion corrections using a Becke-Johnson damping scheme. The bulk lattice constant for Ag used for our slab was determined in our previous study to be 3.891 Å, in reasonable agreement with the experimental value of 4.079. An Ag (111) surface was modeled in this study using a 3 × 3 × 4 slab, where the bottom two layers of the slab were constrained while the top two layers were allowed to relax. A plane-wave energy cutoff of 500 eV is used. Ionic relaxation steps are terminated when the forces on all atoms are less than 0.05 eV/Å. All slab calculations use 4 × 4 × 1 Monkhorst-Pack k-point mesh with >10 Å vacuum spacing between periodic images in the z-direction. For slab and adsorbate configurations, electron orbitals were smeared with a first order Methfessel-Paxton method with a smearing width of 0.2 eV. Gas-phase calculations were performed in a 10 Å 3 box at the gamma point using Gaussian smearing with a smearing width of 0.05 eV.