  Previous simulation and experimental studies have shown that some grain
boundaries (GBs) can couple to applied shear stresses and be moved by them,
producing shear deformation of the lattice traversed by their motion. While
this coupling effect has been well confirmed for symmetrical tilt GBs, little
is known about the coupling ability of asymmetrical boundaries. In this work we
apply a combination of molecular dynamics and phase field crystal simulations
to investigate stress-driven motion of asymmetrical GBs between cubic crystals
over the entire range of inclination angles. Our main findings are that the
coupling effect exists for most of the asymmetrical GBs and that the coupling
factor exhibits a non-trivial dependence on both the misorientation and
inclination angles. This dependence is characterized by a discontinuous change
of sign of the coupling factor, which reflects a transition between two
different coupling modes over a narrow range of angles. Importantly, the
magnitude of the coupling factor becomes large or divergent within this
transition region, thereby giving rise to a sliding-like behavior. Our results
are interpreted in terms of a diagram presenting the domains of existence of
the two coupling modes and the transition region between them in the plane of
misorientation and inclination angles. The simulations reveal some of the
dislocation mechanisms responsible for the motion of asymmetrical tilt GBs. The
results of this study compare favorably with existing experimental measurements
and provide a theoretical ground for the design of future experiments.
