Formation of stacking defects at surfaces: From atomistic simulations to density functional theory calculations

We have performed electronic structure calculations to study the evolution of the stacking fault energy at (111) surfaces of metals. We first apply an sp–d tight-binding model and then increase the accuracy on the electronic structure by using density functional theory (DFT) calculations. We show in this way the relative importance of sp–d hybridization both in the formation of defects at the surface of metals and in reconstruction phenomena as a function of band filling especially at the end of transition metal series. Comparing our results with atomistic simulations it is concluded that although atomistic calculations are powerful tools to investigate relaxation mechanisms at surfaces, a higher degree of accuracy on electronic structure is necessary to quantify the energy of some defects at surfaces like stacking faults. In particular long range interactions associated to less localized sp electrons are playing a rather important role in reconstruction phenomena for metals like platinum and gold. These results are backed up by DFT calculations applied to iridium, platinum and gold (111) surfaces.