Atomistic simulations of structures and mechanical properties of < 011 > tilt grain boundaries and their triple junctions in diamond

Atomic structures, energies, and stress distributions of symmetrical [011] tilt grain boundaries (GB's) and selected GB triple junctions (TJ's) in dia mond as well as a multiply twinned diamond particle have been calculated us ing an analytic bond order potential function. In general, energies of [011 ] tilt GB's are about 1 J/m(2) lower than those for [001] tilt GB's calcula ted with the same analytic potential. Energy ordering for two models of the Sigma = 3(2 (1) over bar 1) GB obtained with the present bond-order potent ial is consistent with results from a tight-binding model. Atomic structure s of selected triple junctions of [011] grain boundaries are modeled and at omic reconstructions within TJ cores that eliminate dangling bonds are sugg ested. Despite a perfect geometrical matching of structural units within th e triple junction cores, excess energies and stresses exist in the vicinity of these structures. Characteristics of atomic stress distributions in mul tiply twinned particles agree with predictions of continuum disclination th eory. [S0163-1829(99)09333-9].