Total energy minimization for diamond (111) surfaces: Support for an undimerized $\pi$-bonded chain reconstruction

A self-consistent linear combination of atomic-orbitals (LCAO) approach to local density theory is used to calculate total energies for the 1 × 1 and various reconstructed 2 × 1 models of the diamond (111) surface. Among the many models suggested, only the Pandey $\pi$-bonded chain model has a lower energy than that of the 1 × 1 surface. A minimum-energy structure is obtained for this model after extensive consideration of relaxations. No dimerization of the surface chain is found to occur.