  A growing number of shock compression experiments, especially those involving
laser compression, are taking advantage of in situ x-ray diffraction as a tool
to interrogate structure and microstructure evolution. Although these
experiments are becoming increasingly sophisticated, there has been little work
on exploiting the textured nature of polycrystalline targets to gain
information on sample response. Here, we describe how to generate simulated
x-ray diffraction patterns from materials with an arbitrary texture function
subject to a general deformation gradient. We will present simulations of
Debye-Scherrer x-ray diffraction from highly textured polycrystalline targets
that have been subjected to uniaxial compression, as may occur under planar
shock conditions. In particular, we study samples with a fibre texture, and
find that the azimuthal dependence of the diffraction patterns contains
information that, in principle, affords discrimination between a number of
similar shock-deformation mechanisms. For certain cases we compare our method
with results obtained by taking the Fourier Transform of the atomic positions
calculated by classical molecular dynamics simulations. Illustrative results
are presented for the shock-induced $\alpha$-$\epsilon$ phase transition in
iron, the $\alpha$-$\omega$ transition in titanium and deformation due to
twinning in tantalum that is initially preferentially textured along [001] and
[011]. The simulations are relevant to experiments that can now be performed
using 4th generation light sources, where single-shot x-ray diffraction
patterns from crystals compressed via laser-ablation can be obtained on
timescales shorter than a phonon period.
