Atomistic simulations of structures and mechanical properties of polycrystalline diamond: Symmetrical < 001 > tilt grain boundaries

Atomic structures and energies of symmetrical [001] tilt grain boundaries ( GB's) in diamond have been calculated over a wide range of misorientation a ngle using a many-body analytic potential, and for some selected short-peri od grain boundaries with tight-binding and first-principles density-functio nal methods. The grain boundary energies from the tight-binding and first-p rinciples methods are about 75% of those calculated with the analytic bond- order potential. The energy rankings of the GB's calculated with the empiri cal potential, however, are similar to that calculated from the tight-bindi ng and the density functional approaches. Atomic-level energy and stress di stributions calculated with the bond-order potential reveal relations betwe en local interface reconstruction and the extent and value of hydrostatic a nd shear stresses. From the calculated local volume strain and hydrostatic stress fields, the atomic bulk moduli are evaluated, and zones of different elastic behavior in the vicinity of the interface are defined. [S0163-1829 (99)08733-0].