FIRST PRINCIPLES SIMULATIONS OF SILICON NANOINDENTATION

Total-Energy pseudopotential calculations are used to study the onset and development of plasticity in nanoindentation experiments. Plastic flow of atoms towards interstitial positions and extrusion of material towards the tip walls, stabilized by the adhesive interactions with t he tip, are the dominant mechanisms. The delocalization of the charge induced by the stress in the elastically compressed structure triggers these plastic deformations. The onset of irreversible damage is relat ed to the plastic deformation of the secund double layer of the Si(111 ) surface.