>Yes. If you integrate over energy, the scattering function factors to a >delta function in time, corresponding to an instantaneous snapshot of the >spatial correlations. It is not a question of Bragg or diffuse scattering.
Actually it is. Bragg scattering is equivalent to projecting all the scattering density in the crystal onto a single unit cell divided by the number of unit cells in the crystal and replicate that average unit cell. In other words, you do a coherent configurational average (over the correlation length of the probe). Furthermore, because Bragg scattering is elastic, you also get a coherent time average. If you Fourier transform all of the scattering function you get the instantaneous local pair-correlation function averaged incoherently over time and space (actually, this is not quite true because you can never measure Q in a diffraction experiment). Paolo Radaelli
