  In this work we study shock-induced plasticity in Mo single crystals,
impacted along the <110> crystal orientation. In particular, the shear
relaxation behind the shock front is quantitatively inspected. Molecular
dynamics (MD) simulations are employed to simulate the deformation during
shock, followed by post-processing to identify and quantify the dislocation
lines nucleated behind the shock front. The information on the dislocation
lines is ensemble averaged inside slabs of the simulation box and over
different realizations of the MD simulations, from which continuous dislocation
fields are extracted using the Discrete-to-Continuous method. The continuous
dislocation fields are correlated with the stress and strain fields obtained
from the MD simulations. Based on this analysis, we show that the elastic
precursor overshoots the shear stress, after which dislocations on a specific
group of slip planes are nucleated, slightly lagging behind the elastic front.
Consequently, the resolved shear stress is relaxed, but the principal lateral
stress increases. The latter leads to an increase in the resolved shear stress
on a plane parallel to the shock wave, resulting in an additional retarded
front of dislocation nucleation on planes parallel to the shock front. Finally,
the two-stage process of plasticity results in an isotropic stress state in the
plane parallel to the shock wave. The MD simulation results are employed to
calculate the dislocation densities on specific slip planes and the plastic
deformation behind the shock, bridging the gap between the information on the
atomic scale and the continuum level.
