APPLICATIONS OF ABINITIO QUANTUM MOLECULAR DYNAMIC RELAXATION - SILICON(111)-5X5 SURFACE RECONSTRUCTION AND ALUMINUM DEPOSITED ON SILICON(100)

We present two applications of a first principles quantum molecular dynamics technique. In the first, we have determined the relaxed atomic geometry and the corresponding electronic structure of the Si (111) surface in the 5 X 5 dimer-adatom-stacking fault structure. We find a unique low temperature behavior for this surface, namely, corrugation of the adatoms on each side of the 5 X 5 unit cell, which we verify by the use of perturbation theory. In a second application, we have determined the relaxed atomic geometry and the corresponding electronic structure of the Al:Si (100) surface in both the 2 X 2 and the 2 X 3 reconstructions. In particular, we find that the Al dimers on this surface are parallel to, rather than perpendicular to, the Si dimer direction.