Solution of Ge(111)-(4×4)-Ag structure using direct methods applied to X-ray diffraction data

A structure model for the Ge(111)-(4×4)-Ag surface is proposed. The model was derived by applying direct methods to surface X-ray diffraction data. It is a missing top layer reconstruction with six Ag atoms placed on Ge substitutional sites in one triangular subunit of the surface unit cell. A ring-like assembly containing nine Ge atoms is found in the other triangular subunit. The stability of the ring assembly may be due to Ge–Ge double bond formation. Trimers of Ge atoms, similar to the trimers found on the Ge(111)-(E3×E3)R30°-Ag surface, are placed in the corners of the unit cell. © 1998 Elsevier Science B.V. All rights reserved.