The Research Of Structure And Properties Of Pd Clusters With Water And Transition Metal Doped

Adsorption and dissociation of H₂O molecule on Palladium clusters were studied using density functional theory. The model systems of Pd4 and Pd7 were chosen. The most stable adsorption site and adsorption energy were systematically calculated for H₂O, OH+H, H₂+O, and O+H+H. The results indicate that the dissociative adsorption is much more stable than that of water molecule. H₂O molecule is most stable on atop site adsorption. For the coadsorption cases, H₂ and OH molecules preferably adsorb on atop or bridge site, and O and H atoms prefer to adsorb on the hollow site. It is also found that the most favorable adsorption sites for the molecular adsorbates ?H₂O, H₂ and OH? are adjacent to the Pd atoms with the largest site-specific polarizabilities. The processes of the adsorption, dissociation, and the dissociative products diffusion of H₂O are analyzed. Moreover, the structural evolution and magnetic properties of MoPdn ?n = 2-14? clusters have been investigated. Extensive search of the lowest-energy structures has been conducted. In the lowest energy structures of MoPdn clusters, the Mo atom gradually moves from an extruded vertex site, to a surface, and to an interior site as the number of Pd atoms increases from 2 to 14. The magnetic moments of Pdn clusters have been enhanced by the doping of Mo impurity for the small sizes of n?6. Larger MoPdn clusters with n?7 are completely nonmagnetic. The quenching of the magnetic moment comes from the electronic and geometric effects for MoPdn clusters. Based on these results, the magnetic properties of 3d and 4d transition-metal ?TM? atoms doped in the chosen sizes palladium clusters ?Pd9 and Pd12? were studied. The magnetic moments for most 3d and 4d TM atoms are completely quenched by the palladium hosts. The significant reduction or complete quenching of magnetism can be understood by the hybridization between the doped TM atom and its neighboring Pd atoms.