Structure determination of the Bi–Ag(111) surface alloy using LEED I–V and DFT analyses

The deposition of 1/3 of a monolayer of Bi on Ag(111) leads to the formation of BiAg2 surface alloy with a long range ordered 3 × 3 R 30 ∘ superstructure. A detailed analysis of this structure using LEED I–V measurements together with DFT calculations is presented. We find strong correlation between experimental and calculated LEED I–V data, with the fit between the two data sets having a Pendryʹs reliability factor of 0.16. The Bi atom is found to replace one top layer Ag atom in each unit cell, forming a substitutional BiAg2 surface alloy, with the Bi atoms residing approximately 0.6 Å above the Ag atoms due to their size difference. DFT calculations are in good agreement with the LEED results.