  When a metallic specimen is plastically deformed, its underlying crystal
structure must often rotate in order to comply with its macroscopic boundary
conditions. There is growing interest within the dynamic compression community
in exploiting x-ray diffraction measurements of lattice rotation to infer which
combinations of plasticity mechanisms are operative in uniaxially shock- or
ramp-compressed crystals, thus informing materials science at the greatest
extremes of pressure and strain rate. However, it is not widely appreciated
that several of the existing models linking rotation to slip activity are
fundamentally inapplicable to a planar compression scenario. We present
molecular dynamics simulations of single crystals suffering true uniaxial
strain, and show that the Schmid and Taylor analyses used in traditional
materials science fail to predict the ensuing lattice rotation. We propose a
simple alternative framework based on the elastoplastic decomposition that
successfully recovers the observed rotation for these single crystals, and can
further be used to identify the operative slip systems and the amount of
activity upon them in the idealized cases of single and double slip.
