A structural identification of the reconstructed system Ni(100) + (2 × 2)C is given by comparing the measured surface phonon dispersion with that calculated in two structural models consistent with the diffraction pattern. The agreement obtained in one of the two cases favours a structural assignment at variance with the LEED determination. The properties of distorsive phase transitions, in terms of a frozen surface phonon, are analyzed. The crucial role of the totally symmetric phonon present at the centre of the Brillouin zone of the reconstructed phase, shown to originate from the frozen phonon at the Brillouin zone edge in the unreconstructed system, is analyzed. The analytic variations of the phonon frequencies with parametric distortion are obtained. An upper limit is deduced for the size of the reconstruction induced distortion from the vibrational data. It is found to be smaller than the estimate derived from LEED measurements.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Condensed Matter Physics
- Surfaces and Interfaces