Origin of site preference of CO and NO adsorption on Pd(1Â 1Â 1) at different coverages: A density functional theory study

► Favorable adsorption sites of CO and NO on Pd(1 1 1) at different coverages. ► Comparison between calculated and experimental vibrational frequencies. ► Physical origin of site preference of CO and NO at different coverages. ► Correlation between adsorption energy and surface coverage.