Atomic and electronic structure of pyrrole on Ge(100)

We have performed ab initio pseudopotential density-functional calculations for pyrrole adsorbed on die Ge(100) surface in order to investigate its atomic and electronic structure. A large number of the pyrrole/Ge(100) adsorption configurations that could result from cycloadditions and Lewis acid-base reactions were examined. The configuration with both Ge - N and Ge - C linkages was found to be the most stable. The Ge - N linkage is formed by dative bonding after N - H dissociation, and the Ge - C linkage is a weak chemical interaction leading to the loss of aromaticity from the pyrrole ring. The pyrrole molecule bridges two down-Ge atoms in adjacent Ge dimer rows. This configuration was used to explain the experimental scanning tunneling microscopy (STM) images.