Ensemble and ligand effects on the acetylene adsorption on ordered PdxAg1−x/Pd(100) surface alloys investigated by periodic DFT study

Abstract

The interactions of acetylene with structurally ordered Pd_xAg_1−x/Pd(100) (x = 1, 0.75, 0.5, 0.25) surface alloys, in which Ag is presented only in the first layer as the computational model system, were investigated by gradient corrected periodic density functional calculations to unravel and understand contributions from electronic strain, electronic ligand and geometric ensemble effects. The calculated adsorption energies indicate that the hollow sites are always found to be more stable than any others and more sensitive to the Ag atoms because of the strong ensemble effect. However, the ligand effect plays a significant role in both the top and bridge adsorption sites. The electrons transferred to the acetylene molecules from the surface increase with increasing concentration of the surface atomic Ag.