Theoretical study of the adsorption of silver atoms on the (111) face of silicon

The adsorption of one or many silver atoms on a (111) silicon face (reduced to 61 dangling atomic orbitals) is investigated by means of a self-consistent Hartree–Fock method parametrized from atomic and thermodynamical data. The valley sites (above three Si atoms) are favored over the top sites (above one Si atom). The extrapolation of the results obtained for several structures corresponding to the adsorption of n = 1, 2, 3, 4, 6, and 7 Ag atoms allows us to conclude that the most stable structures correspond: for documentclass{article}pagestyle{empty}begin{document}$ theta = frac{1}{3} $end{document} to linear Ag chains (3 × 1 phase), for documentclass{article}pagestyle{empty}begin{document}$ theta = frac{2}{3} $end{document} to an honeycomb lattice (documentclass{article}pagestyle{empty}begin{document}$ sqrt 3 times sqrt 3 $end{document} phase), and for θ = 1 to a centred hexagonal lattice (documentclass{article}pagestyle{empty}begin{document}$ sqrt 3 times sqrt 3 $end{document} phase), the Ag atoms located at the centers of the hexagons being beneath the plan of the hexagons. The adsorption energies corresponding to the various θ are practically equal (ca. 3 eV/Ag). The net charges of Ag atoms are equal to 0.35.