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 diamond as well as a multiply twinned diamond particle have been calculated using an analytic bond order potential function. In general, energies of 〈011〉 tilt GB’s are about 1 ${\mathrm{J}/\mathrm{m}}^2$ lower than those for 〈001〉 tilt GB’s calculated with the same analytic potential. Energy ordering for two models of the $\Sigma =3\left(2\mathrm{}1\mathbf{¯}1\right)$ GB obtained with the present bond-order potential is consistent with results from a tight-binding model. Atomic structures of selected triple junctions of 〈011〉 grain boundaries are modeled and atomic reconstructions within TJ cores that eliminate dangling bonds are suggested. Despite a perfect geometrical matching of structural units within the triple junction cores, excess energies and stresses exist in the vicinity of these structures. Characteristics of atomic stress distributions in multiply twinned particles agree with predictions of continuum disclination theory.