Tight-binding study of hydrogen on the C(111), C(100), and C(110) diamond surfaces

The band structure, total energies, and relaxed geometries are calculated for the C (111), C (100), and C (110) surfaces using a parametrized tight-binding model for carbon. The method and addition of C-H parameters to the model are described in detail. Results for the bare and hydrogenated C (111) surfaces are used to compare the accuracy of the method with ab initio techniques. A stable hydrogenated (21) reconstructed surface is found, which resembles the C (110) surface. Removal of one H atom from the dihydride C (100) results in a 3/2 hydride surface, where the odd hydrogen is bonded equally to two surface carbons. Although the fully H-covered C (100) (21) surface has a clean gap, the partially covered surface has a half-filled state, consistent with photoemission data. The geometries and H vibrations are also presented for the C (110) surface. The surface chains on the bare C (110) have bond lengths close to graphite and dimerize from a Peierls distortion. Addition of H to this surface restores the bond lengths to approximately that of bulk diamond. Comparison of the band structures and H vibrations with experiment helps identify the nature of the hydrogen coverage on the surfaces.