High-resolution electron-energy-loss spectroscopy was used to investigate the dispersion of surface phonons on the unreconstructed (1 x 1) and the reconstructed (5 x 1) Ir(100) surface. A significant difference in the dispersion properties of the (1 x 1) and (5 x 1) surfaces was found for both the [011] and the [001] direction. Lattice-dynamical calculations in a second-nearest-neighbour force-constant model fit the experimental results on the (1 x 1) surface if a large amount of surface stress was invoked. The results suggested that the surface stress was the driving force for the surface reconstruction of Ir(100)-(1 x 1)→Ir(100)-(5 x 1).

Surface-Phonon Dispersion Investigation of the (1 x 1) → (5 x 1) Reconstruction of the Ir(100) Surface. S.Lehwald, J.G.Chen, G.Kisters, E.Preuss, H.Ibach: Physical Review B, 1991, 43, 3920-7