Surface mismatch and stress relief mechanisms at metallic surfaces

In the framework of a tight binding model within the second moment approximation (TB-SMA), we show that due to the reduced number of chemical bonds, a large lattice mismatch can exist between the surface lattice parameter and the bulk one on the (1 1 1) surfaces of pure metals. The behavior of this latter quantity, referred as surface mismatch and obtained by minimizing the surface site energy, can be explained from considerations on the relative range of the repulsive part of the interatomic potential with respect to the attractive one. The link between the large surface mismatch for Au and Pt and their (1 1 1) surface reconstructions as well as the strong dependence of the atom–atom bond lengths with the size of epitaxial islands are discussed.