  Dislocations are topological defects known to be crucial in the onset of
plasticity and in many properties of crystals. Classical Elasticity still fails
to fully explain their dynamics under extreme conditions of high strain
gradients and small scales, which can nowadays be scrutinized. In such
conditions, corrections to the Volterra dislocation fields and to the
Peach-Koehler force, for example, become relevant. One way to go beyond the
Volterra solution is to consider other terms in the total Laurent series
solution. This is the so called core field. One of its consequences is to
predict a driving force on the dislocation due to background strain/stress
gradients, which has also been suggested by other core energy calculations.
Here we confirm its existence by presenting a direct observation of strain
gradients driving edge dislocations in 2D atomistic simulations. We show that,
in systems with scale invariance, the results for such core force can be used
to obtain the total core energy, allowing a standard value for this energy to
be compared with other classical methods of obtaining it. The force measured in
our system differs from the prediction obtained by a direct core field
analysis. Moreover, we found that higher order gradients of strains can also
act as relevant forces.
