Peak positions and shapes in neutron pair correlation functions from   powders of highly anisotropic crystals
  The effect of the powder average on the peak shapes and positions in neutron pair distribution functions of polycrystalline materials is examined. It is shown that for highly anisotropic crystals, the powder average leads to shifts in peak positions and to non-Gaussian peak shapes. The peak shifts can be as large as several percent of the lattice spacing. 
D. A. Dimitrov, H. Roder, and A. R. Bishop