Hydrogen vibrations at transition metal surfaces

Abstract

Chemisorbed hydrogen has been studied on a variety of simple and composite transition metal surfaces using local density functional calculations. The goal of these studies is to elucidate trends and general principles in bond energies, atomic geometries, vibrational frequencies, and dynamic effective charges. The theoretical approach, based on the linear augmented plane wave method, will be reviewed. Results will be discussed for H in 2-, 3-, and 4-fold sites on W(001), Ru(0001), Cu(111), Pt(111), Rh(001), and the metal overlayer systems Cu-Ru(0001) and Ni-W(001). In most cases, all the harmonic vibrational modes were studied. Some anharmonic effects were examined. While good agreement has been obtained with much of the available experimental data, some outstanding disagreements will be discussed. Our results will be compared with the nearest-neighbor harmonic potential model and effective medium approach.