1ST-PRINCIPLES PHONON AND MULTIPLE-SCATTERING ELECTRON-ENERGY-LOSS-SPECTRA STUDIES OF CU(111) AND AG(111)

Parameter-free first-principles phonon calculations are used in conjunction with multiple-scattering electron-energy-loss calculations to reveal new localized modes on Cu(111) and Ag(111). The discovery of these z-polarized localized modes along GAMMAMBAR and GAMMAKBAR provides for the first time good agreement between theory and all the existing helium-atom-scattering and electron-energy-loss experimental results. The new results indicate that it is not necessary to evoke exotic models such as anomalous surface dynamical effects on these densely packed surfaces.