Green function theory of chemisorption on sp-hybrid crystals

A self-consistent Green function calculation of the adatom charge transfer (Δq) and the chemisorption energy (ΔE) is performed for hydrogen and the halogens on Si and Ge substrates, which are modeled by sp-hybrid orbital chains. The effect of Shockley surface states on the hydrogen chemisorption process is studied in some detail. From the chemisorption point of view, the behaviour of Si resembles that of Ge, the (111) surfaces having a smaller value of |ΔE| than the (100) ones for all the adsorbates considered. In the case of the halogens, the strong reactivity of fluorine is confirmed by the large values obtained for Δq and |ΔF|.