An ab initio study of silver-titanium interfaces in gas-phase and surface-supported clusters

The TiAg interface is studied via density-functional theory calculations by considering different systems, ranging from free gas-phase clusters to small clusters supported on Ti(0001) and to an Ag monolayer on the same surface. Our results reveal that Ag impurities preferentially occupy surface sites over bulk or subsurface ones in Ti clusters and on the Ti(0001) surface, with the exception of icosahedral geometries where they are centrally incorporated due to local stress relief. For the gas-phase clusters, Ti@Ag core@shell arrangements are significantly more stable than their Ag@Ti counterparts, supporting the formation of chemically ordered arrangements. For surface-supported systems, small Ag clusters (up to tetramers) exhibit non-trivial adsorption behaviors. Ag clusters favor fcc over hcp stacking on Ti(0001); however, bulk-like stacking is obtained for complete monolayer adsorption. We further demonstrate that the adhesion between Ag and Ti is strong, with an adhesion energy of 2.4 J m^-2, significantly stronger than that of Ag on Ti oxides. The charge analyses show that Ag adatoms gain charges from the Ti(0001) surface, and as the Ag cluster size increases, the net charge per Ag atom becomes progressively less negative. Our findings reveal that Ag and Ti can form sharp and well-defined interfaces with limited intermixing. These insights are relevant in the design of functional Ag coatings on Ti-based nanostructures for biomedical and electronic applications, where both mechanical robustness and interfacial stability are crucial.