Classical trajectory calculations were employed to study diamond (100) surface reconstructions. Atomic forces were computed from two types of potential-energy functions. A quantum mechanical potential based on the semiempirical PM3 (parametric method number three) Hamiltonian was used to describe the central core of the surface model, while an empirically parametrized potential was developed to extend the size of the model surface. The results indicate that the most energetically favorable surface consists of alternating monohydride dimers and dihydride sites. The global topology of reconstructed (100) surfaces can include dimer rows and zigzag dimer sites. The two configurations are close in energy, for both dehydrogenated and monohydride surfaces, with the row configuration being slightly more favorable. The minimum-energy dehydrogenated (100) diamond surface was found to consist of dimers with biradical electronic structures. The presence of atomic-level steps was found to prevent the formation of nearby dimer bonds, even when each of the available carbon atoms has a free valence.

• Received 8 November 1993

DOI:https://doi.org/10.1103/PhysRevB.49.5662