Density functional study of ethylene adsorption on small gold, palladium and gold-palladium binary clusters

Density functional theory calculations were performed to investigate the structural and energetic properties of chemisorbed Au_n-(C₂H_4)x and Pd_n-(C₂H_4)x complexes, with n = 2 - 4 and x = 1 - 4. Adsorption in π-bonded mode dominates in Au_n-(C₂H_4)x species irrespective of x while the di-σ mode can be formed in the most stable Pd_n-(C₂H_4)x species. The adsorption energy decreases as the number of C₂H₄ molecules increases in Au_n-(C₂H_4)x with n≤slant 4 and Pd_n-(C₂H_4)x with n≤slant 3. The adsorption of one C₂H₄ molecule on bimetallic Au/Pd clusters has also been studied. The C₂H₄ molecule prefers binding to Pd atoms in π-bonded configuration on Au/Pd clusters. The net charge transfer and the typical shift in the vibrational frequencies of C₂H₄ have also been determined and discussed.