  When compressed, a metallic specimen will generally experience changes to its
crystallographic texture due to plasticity-induced rotation. Ultrafast x-ray
diffraction techniques make it possible to measure rotation of this kind in
targets dynamically compressed over nanosecond timescales to the kind of
pressures ordinarily encountered in planetary interiors. The axis and the
extent of the local rotation can provide hints as to the combination of
plasticity mechanisms activated by the rapid uniaxial compression, thus
providing valuable information about the underlying dislocation kinetics
operative during extreme loading conditions. We present large-scale molecular
dynamics simulations of shock-induced lattice rotation in three model crystals
whose behavior has previously been characterized in dynamic-compression
experiments: tantalum shocked along its [101] direction, and copper shocked
along either [001] or [111]. We find that, in all three cases, the texture
changes predicted by the simulations are consistent with those measured
experimentally using in situ x-ray diffraction. We show that while tantalum
loaded along [101] and copper loaded along [001] both show pronounced rotation
due to asymmetric multiple slip, the orientation of copper shocked along [111]
is predicted to be stabilized by opposing rotations arising from competing,
symmetrically equivalent slip systems.
