  Emergent grain boundaries at free surface control material properties such as
nanomaterial strength, catalysis, and corrosion. Recently the restructuring of
emergent boundaries on copper (111) surfaces was discovered experimentally and
atomic calculations point to its universality in fcc metal systems.
Restructuring is due to a preference for boundaries to shift their tilt axis
across the (1-10) plane towards [112] and ultimately to form low energy [112]
core shifted boundaries (CSBs). However, the observed geometry of these
emergent boundaries is not reproduced by atomic calculations and the driving
force is still controversial due to inconsistencies between the computational
continuum analysis and atomic calculations. Here, using atomic calculations
that involve a methodical shift of the dislocation core, we confirmed the core
shift of emergent boundaries observed in experiment and reconciled the atomic
calculations with the elastic analysis through the inclusion of a straight
wedge disclination at the free surface.
