  We derive a continuum-level plasticity model for polycrystalline materials in
the high energy density regime, based on a single dislocation density and
single mobility mechanism, with an evolution model for the dislocation density.
The model is formulated explicitly in terms of quantities connected closely
with equation of state (EOS) theory, in particular the shear modulus and
Einstein temperature, which reduces the number of unconstrained parameters
while increasing the range of applicability. The least constrained component is
the Peierls barrier $E_P$, which is however accessible by atomistic
simulations. We demonstrate an efficient method to estimate the variation of
$E_P$ with compression, constrained to fit a single flow stress datum. The
formulation for dislocation mobility accounts for some or possibly all of the
stiffening at high strain rates usually attributed to phonon drag. The
configurational energy of the dislocations is accounted for explicitly, giving
a self-consistent calculation of the conversion of plastic work to heat. The
configurational energy is predicted to contribute to the mean pressure, and may
reach several percent in the terapascal range, which may be significant when
inferring scalar EOS data from dynamic loading experiments. The bulk elastic
strain energy also contributes to the pressure, but appears to be much smaller.
Although inherently describing the plastic relaxation of elastic strain, the
model can be manipulated to estimate the flow stress as a function of mass
density, temperature, and strain rate, which is convenient to compare with
other models and inferences from experiment. The deduced flow stress reproduces
systematic trends observed in elastic waves and instability growth experiments,
and makes testable predictions of trends versus material and crystal type over
a wide range of pressure and strain rate.
