CORRELATION CALCULATIONS FOR THE RECONSTRUCTION OF THE SI(100) SURFACE

Ab initio multi-reference configuration interaction calculations are p erformed for the Si(100) surface using a cluster approach. The converg ence with respect to the cluster size is checked and the final results are taken from a Si32H28 cluster which models two dimers and six bulk layers. We find for the ideal as well as for the p(1 x 2) reconstruct ion a singlet ground state consisting of several configurations. The e nergy gain due to forming the symmetric dimer in the p(1 x 2) structur e is 1.75 eV, the bond length of the dimer is 2.35 Angstrom, which is very close to the bulk value. In contradiction to the local density ap proximation results and in agreement with previous correlation calcula tions we do not find an asymmetric p(1 x 2) structure. (C) 1998 Elsevi er Science B.V. All rights reserved.