A theoretical study of C2H2 adsorption on the Ge(0 0 1) surface

Using a first-principles pseudopotential technique, we have investigated the adsorption of C2H2 on the Ge(0 0 1) surface. We have found that, at low temperatures, the di-σ bond configuration is the most stable structure from the energetic point of view. According to our calculations, it is not possible to conclude if C2H2 adsorbs preferentially on alternate or adjacent dimer sites. The di-σ adsorbed system is characterized by symmetric and slightly elongated Ge–Ge dimers, and by a symmetric C–C bond with length close to the double carbon bond length of the ethylene molecule. Our total energy calculations suggest that other meta-stable configurations, like the 1,2-hydrogen transfer model, are also possible. This behaviour was also observed for the silicon based system. In addition, we present theoretical scanning tunneling microscopy images and calculated vibrational modes for the adsorbed system with a view to contribute to further experimental investigations.