The diffusion pathways between the trough and the dimer row on the Si(100) surface are investigated by tight-binding molecular dynamics calculations using the environment-dependent tight-binding silicon potential and by ab initio calculations using the Car-Parrinello method. The studies discover a new diffusion pathway consisting of the rotation of the ad-dimer. The calculated energy barrier is in excellent agreement with experiment and is much more energetically favorable than other diffusion pathways by parallel and perpendicular ad-dimers.

• Received 24 July 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.5872