First-principles calculations of energetics and electronic structure for reconstructed Si(111)-(5 x n)-Au surfaces

We report results of ab initio calculations with various exchange-correlation functionals for the Si(111) surface with a 0.6-monolayer Au decoration. Seven different variations of the recently developed Erwin-Barke-Himpsel and Abukawa-Nishigaya models are studied in detail. Atomic geometries are determined by total-energy minimizations. We find the Erwin-Barke-Himpsel model of the Si(111)-(5 x 4)-Au surface with one Si adatom per unit cell to be the most favorable structure. Seven-member rings and undercoordinated Si atoms of the Abukawa-Nishigaya model are unstable. Scanning tunneling images and band structures are calculated for the controversial geometries. For the (5 x 4) adatom geometry the resulting electronic structure agrees with the available experimental data.