The interactions of acetylene with structurally ordered PdxAg1-x/Pd(100) (x = 1, 0.75, 0.5, 0.25) surface alloys, in which Ag is presented only in the first layer as the computational model system, were investigated by gradient corrected periodic density functional calculations to unravel and understand contributions from electronic strain, electronic ligand and geometric ensemble effects. The calculated adsorption energies indicate that the hollow sites are always found to be more stable than any others and more sensitive to the Ag atoms because of the strong ensemble effect. However, the ligand effect plays a significant role in both the top and bridge adsorption sites. The electrons transferred to the acetylene molecules from the surface increase with increasing concentration of the surface atomic Ag.

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Osmium (Os) is a hexagonal-close-packed metal with a non-spherical Fermi surface that seriously deviates from the assumption in the Mayadas-Shatzkes electrical-resistivity model (MS model) for the size effects of polycrystalline films of metals due to electron scattering by grain boundaries. In this work, we studied the resistivity of the Os films with different thicknesses as a function of temperature in the range of 20 to 296 K. The electron scattering by the surface was found to be unimportant in the contributions to the size effects of resistivity of Os films with a sufficient thickness. Based on the first-principles calculations, an analytical equation was suggested for correction to the MS model and used for fitting the temperature-dependent resistivity of the Os films. The results show that correction to the MS model is necessary and the residual resistivity caused by the defects and impurities cannot be neglected. In addition, the inhomogeneity of resistivity in the direction perpendicular to the film surface was discussed under an assumption of parallel circuits.

Twenty-five kinds of Palladium-silver alloy stepped surface models are established based on the pure Pd(211) stepped surface system. The surface energies, work function, d-band center and the d-band local density of states (d-LDOS) on these different Palladium-silver alloy stepped surface configurations were investigated using the generalized gradient approximation (GGA) of density functional theory (DFT). The calculation results show that both the concentration and position of the doped Ag atoms have effect on these four surface parameters. The surface stability is weakened with increase of the concentration of the doped Ag atoms. The work function is more sensitive to the position of Ag atoms than the Ag concentration, while the surface energy is more depended on the Ag concentration. The substitution of Pd atoms by Ag on the pure Pd(211) stepped surface leads to the reduction of the work function. On the other hand, the d-band center of the surface Pd atoms shifts to the Fermi energy level when the Ag atoms substitute the Pd atoms in the third layer. Furthermore, the magnitude of the surface Pd d-band center increases with the content of Ag atoms from the bottom to the top along the stepped surface, and the bonding activity of the surface Pd atoms enhances. The further d-LDOS analysis shows that the Pd d-electronic structure changed with the substitution by Ag atoms on the stepped surface.