  By following the trajectories of quantum particles inside a periodic lattice
and preserving their classical probabilities for reflection, transmission and
absorption at each lattice plane, classical scattering outcomes are obtained.
Diffraction phenomena in crystals are reproducible after assigning probability
amplitudes to every classical outcome. When applied to X-ray diffraction in
reflection geometry, this procedure has provided simple recursive equations to
calculated the X-ray reflectivity of crystals with thickness varying since a
few atomic layers to infinity. The results are in agreement with the dynamical
theory of X-ray diffraction, even when absorption is considered.
