Anomalous dynamical behavior of the Cu(110) surface

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Abstract
The thermal vibrations of surface atoms on Cu(110) have been studied as a function of temperature with ion-scattering spectroscopy in the impact-collision mode. By comparing the experimental data to Monte Carlo simulations of the scattering process, mean-square displacements of surface atoms are obtained that agree well with the results of helium diffraction and inverse photoemission experiments. Below 550 K the atom vibrations can be described quite well by a Debye temperature of 224 K obtained from phonon slab calculations. Above 550 K, strong anharmonic vibrations are observed. In this temperature region we find thermally activated adatoms to be produced with an activation energy of 0.27±0.07 eV. Both effects lead above 1000 K to structural changes of the surface that can be described in terms of a rough surface or a quasiliquid layer on the surface.