Studies of the atomic and electronic structures of Pd clusters with 2-23, 55, and 147 atoms have been carried out using the ultrasoft pseudopotential plane wave method and the spin-polarized generalized gradient approximation for the exchange-correlation energy. We find predominantly an icosahedral growth in these clusters, and size dependent oscillatory magnetic moments that are not confined just to the surface atoms. Atomically closed shell 13-, 55-, and 147-atom clusters have large moments of $0.61{\mu }_B/\mathrm{atom},$ $0.47{\mu }_B/\mathrm{atom},$ and $0.41{\mu }_B/\mathrm{atom},$ respectively. But cubic ${\mathrm{Pd}}_{55}$ isomer has a low moment of $0.18{\mu }_B/\mathrm{atom}$ only, indicating the importance of the icosahedral structure in the development of magnetism in Pd clusters. The evolutions of the $\mathrm{sp}-d$ hybridization, the magnetic moment and the electronic structure are discussed as a function of the cluster size. The magnetic energy is found to be small. Further studies on the adsorption of H and O show that though both an increase as well as a decrease of the moment are possible, often there is a reduction in the magnetic moments of Pd clusters. A hydrogen induced metal to nonmetal transition is predicted in ${\mathrm{Pd}}_6{\mathrm{H}}_8$ and ${\mathrm{Pd}}_{13}{\mathrm{H}}_8$ clusters.

• Received 20 June 2002

DOI:https://doi.org/10.1103/PhysRevB.66.144413