SPATIAL DISTRIBUTION OF ATOMS IN GAS-COVERED Pd-X NANOPARTICLES (X=Ag, Cu, Ni, Pt)

A Monte-Carlo (MC) simulation procedure has been developed where the pair bond energies are allowed to take into account the various coordination numbers of surface atoms and the presence of adsorbates. The pair bond energies are calculated from partial bond energies of atoms which, in turn, are calculated from modified tight binding model in the second moment approximation. The model has been applied to study the role of adsorption of hydrogen, oxygen, carbon monoxide and nitric oxide on the surface composition and surface bond geometry of bimetallic Pd-X(X=Ag, Cu, Ni, Pt) nanoparticles having fcc cubo-octahedral geometry with 586 atoms. The results are compared with the known experimental results. Importance of the results in studying reactions on supported bimetallic catalysts has been highlighted.