Density functional theory studies of the palladium-silver(211) stepped surfaces

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.