The diffusion pathways between troughs and the dimer rows on the (100) surface were investigated by using tight-binding molecular dynamics calculations, involving an environment-dependent tight-binding potential and ab initio calculations based upon the Car-Parrinello method. This revealed a new diffusion pathway which consisted of rotation of the ad-dimer. Such a diffusion process was more energetically favorable than was diffusion via translation of the parallel and perpendicular ad-dimers. The barrier in a diffusion pathway which involved rotation was determined not simply by the breaking of bonds, but was also affected by the stresses between the ad-dimer and the surface dimers. The calculated energy barrier was in excellent agreement with experiment and was much more energetically favorable than those for diffusion involving parallel and perpendicular ad-dimers.

Ad-Dimer Diffusion between Trough and Dimer Row on Si(100) G.D.Lee, C.Z.Wang, Z.Y.Lu, K.M.Ho: Physical Review Letters, 1998, 81[26], 5872-5