Shear deformation kinematics of bicrystalline grain boundaries in atomistic simulations

The shear deformation behavior of bicrystalline grain boundaries is analyzed using continuum mechanical metrics extracted from atomistic simulations. Calculating these quantities at this length-scale is premised on determining the atomic deformation gradient tensor using interatomic distances. Employing interatomic distance measurements in this manner permits extension of the deformation gradient formulation to estimate important continuum-scale quantities such as lattice curvature and vorticity. These continuum metrics are calculated from atomic deformation fields produced in 2D and thin 3D equilibrium bicrystalline grain boundary structures under shear at 10 K. Results from these simulations show that interface structure strongly influences the resulting accommodation mechanisms under shear and deformation fields produced in the surrounding lattice. Calculating these continuum quantities at the nanoscale lends insight into localized and collective atomic behavior during shear deformation for various mechanisms, and it is shown that different mechanisms lead to differing behavior. Additionally, the results of these calculations can perhaps serve as an intermediary form to inform continuum models seeking to explore larger-scaled grain boundary deformation behavior in 3D, and to evaluate the veracity of continuum models that overlap the nanoscale.