Ab Initio Calculations for Br and Cl adsorption on the Ag(100) surface

Ab-initio density-functional methods have been used to find the ground-state configurations of Br and Cl adsorbates on Ag(100) surfaces with coverages of $1/9$, $2/9$, $1/4$, $1/3$, and $1/2$ monolayers. The supercell slab method was used to calculate the electron-density distributions for each configuration. The charge-transfer function, surface dipole moments, adsorbate resident charge, and adsorption energies were calculated and compared with results from electrochemical adsorption exeperiments and Monte Carlo simulations. The lateral adsorbate-adsorbate interactions and the binding energies were extracted from the adsorption energies using a lattice-gas model. The calculated quantities are weakly dependent on the coverage, and the overall shape of the charge-transfer function is nearly coverage independent.