The Origin and Possible Implications of Surface Stress on Metals

The origin of surface stress on metals is discussed. Self-consistent pseudo-potential calculations of the surface stress tensor at the aluminium [111] and [110] surfaces are reported. In both cases the stress is tensile, favouring contraction in the plane of the surface. The results for aluminium are compared with those for jellium and a simple interpretation is developed in terms of the smoothing of the electronic wavefunctions at the crystal surface. Some implications of the presence of a surface stress for surface phonon dispersion and for surface instabilities are discussed.