An ab initio investigation of the Si(111)-(7 x 7) surface reconstruction was undertaken using the state of the art in massively parallel computation. Calculations of the total energy of an ∼700 effective-atom super-cell were performed to determine the fully relaxed atomic geometry, the scanning-tunnelling-microscopic images as a function of bias voltage and the energy difference between the (7 x 7) and the (2 x 1) reconstructions. The (7 x 7) reconstruction was found to be energetically favourable to the (2 x 1) surface by 60meV per (1 x 1) unit cell.

Ab initio Theory of the Si(111)-(7 x 7) Surface Reconstruction - a Challenge for Massively Parallel Computation. K.D.Brommer, M.Needels, B.Larson, J.D.Joannopoulos: Physical Review Letters, 1992, 68, 1355-8