The Si (100) surface. II. A theoretical study of the relaxed surface

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Abstract
The potential, charge density, and energy spectrum are calculated self-consistently for a Si (100) surface for which the first layer of atoms is relaxed towards the interior of the crystal by 0.17 Å. In addition to the two bands of surface states which are calculated to reside in the absolute energy gap of the ideal (unrelaxed unreconstructed) surface, two new bands of surface states which overlap the valence band, and one new band which lies beneath it, appear. These new bands are caused by the strengthening of the back bonds. We examine in some detail the response of the valence charge distribution to the inward motion of the surface atoms. We also document the utility of using linear-response theory to describe the change in the potential caused by motion of the surface atoms. Finally, we use the linear-response method to produce a potential which corresponds to relaxing the surface atoms by another 0.28 Å towards the bulk and calculate the energies of the absolute gap surface states and that of the new band of lowest energy.