High-resolution electron energy loss spectroscopy analysis of Ag(001): discovery of a new surface longitudinal mode using first-principles phonon calculations

We present analysis of electron-energy loss spectra of Ag(001) using first-principles surface phonon and multiple scattering inelastic cross-section calculations. Excellent agreement with experiment is obtained. The study reveals a new longitudinal surface phonon at MBAR which causes the measured loss peak to shift as the incident energy is varied. These results demonstrate the importance of using accurate theory for proper interpretation of EELS spectra and indicate that force-constant models with adjustable parameters may be misleading.