THE ADSORPTION OF HYDROGEN ON PD(100) AND RH(100) SURFACES - A COMPARATIVE THEORETICAL-STUDY

Hydrogen adsorption on Pd(100) and Rh(100) surfaces is considered theo retically within the framework of total-energy calculations using the all-electron full-potential LMTO method. The binding energy, the equil ibrium geometry, the top-layer relaxations as well as the work functio ns are calculated for hydrogen adsorption at the surface hollow site a nd into subsurface positions at Pd(100) and Rh(100) surfaces. It is fo und that for Pd, the hydrogen prefers a surface site to a subsurface p osition, which is again more favorable than a bulk interstitial site, The binding energy is positive for each of these positions. For Rh, bo th the subsurface and bulk position have a negative binding energy.