Ab initio multi-reference configuration interaction calculations were performed for the Si(100) surface using a cluster approach. The convergence with respect to the cluster size was checked and the final results were taken from a Si32H28 cluster which models two dimers and six bulk layers. For the ideal, as well as for the p(1 x 2) reconstruction, a singlet ground state was found which consisted of several configurations. The energy gain due to forming symmetrical dimers in the p(1 x 2) structure was 1.75eV, the bond length of the dimer was 2.35Å (which was very close to the bulk value). In contradiction to the local density approximation results and in agreement with previous correlation calculations, no asymmetrical p(1 x 2) structure was found.

Correlation Calculations for the Reconstruction of the Si (100) Surface. B.Paulus: Surface Science, 1998, 408[1-3], 195-202

2 x 1 Reconstruction of Si (100)