A structural analysis of a clean (100) Cu surface, using low-energy electron diffraction techniques, revealed an unexpected in-plane lattice contraction of about 1%; as compared with the bulk lattice parameter. That is, there was a surface reconstruction which was associated with tensile stress in the surface. This was relevant to the epitaxial growth of other metals on Cu(100).

S.Müller, A.Kinne, M.Kottcke, R.Metzler, P.Bayer, L.Hammer, K.Heinz: Physical Review Letters, 1995, 75[15], 2959-62