First-principles study of sulfur multi-absorption in nickel and its segregation to the Ni(100) and Ni(111) surfaces

It is of both experimental and fundamental interest to understand the sulfur (S) properties of metallic alloys. Therefore, in this work, we present the physical and chemical properties of sulfur in Ni-fcc solid solution and its chemisorption on the Ni(100) and Ni(111) surfaces using the density functional theory. It is shown that the substitutional site is more stable than the interstitial sites because of a significant “vacancy-sulfur” interaction and steric effects. The migration mechanism of S atoms in a solid solution is presented in detail, and our results are compared to the experimental data. We also discuss the interactions between sulfur and the vacancies. Adsorption of S on the Ni(100) and Ni(111) surfaces arises preferably on the most coordinated sites. A large segregation energy is calculated for the Ni(100) and Ni(111) surfaces.