First-principles Study of Ag Stripe Formation on the Ni(110) Surface

The stability of monolayer-thick Ag stripes formed on the Ni(110) surface was studied using first-principles calculations. The Ag stripes were found to be the aggregation of one-dimensional (1-D) silver (Ag) clusters along the [110] direction between the Ni(110) rows, and the clusters extended in the [001] direction to form stripes. Due to the large lattice mismatch between the adsorbed Ag and the Ni substrate, 1-D Ag clusters were not stable with more than seven atoms, and the edge atoms at the 1-D clusters tended to dissociate. The diffusion barriers for the dissociation of the 1-D Ag cluster edges were evaluated using the nudged elastic band method and found to be 0.41 eV for a two-Ag atom cluster (n = 2) and 0.14 eV for a ten-Ag atom cluster (n = 10). Considering surface relaxation of the substrate Ni atoms in the ⟨001⟩ directions, the diffusion barrier further decreased by ∼0.06 eV, which explains the experimental scanning tunneling microscopy images. It was also found that 1-D Ag clusters aggregated to form stripes extending in the [001] direction due to the effect of substrate strain and the one dimensional band formation of Ag 5s-derived states in the stripe direction.