The structure of the diamond (111) surface—a SLAB-MINDO study

Abstract

Abstract In this paper we have investigated the reconstruction of the diamond (111) surface via the SLAB-MINDO method. Several π-bonded chain models which have been proposed in the literature have been examined. Since the diamond (111) surface actually shows a 2 × 2 LEED pattern, and the cleaved surface is hydrogen terminated, we have also studied the stability of the 2 × 2 surface unit cell, the triple bond cleavage surface and the effect of hydrogen chemisorption. For the single bond cleavage surface we predict that both a dimerized and non-dimerized π-bonded chain model topology will occur. For the triple bond cleavage surface we find that a non-dimerized single chain model with a small degree of buckling has the lowest energy. Calculations employing 2 × 2 surface unit cells to represent both single and triple bond cleavage surfaces always reverted to a 2 × 1 topology. Thus we have found no evidence for a 2 × 2 surface symmetry as an explanation of the 2 × 2 LEED pattern. The single and triple bond cleavage energies for the clean diamond (111) surface have been calculated and a single bond cleavage mechanism determined to be more energetically favored. When hydrogen chemisorption is included into the cleavage process, however, we find that triple bond cleavage of this particular surface may in fact occur.