Should be found out:
– Scattering cross-section according to Kinematic Scattering
– Comparing it with the one derived by van den Hulst
– Find general series expansion for K(w) and then calculate Q_abs, subsequently Q_sca in general form

Is phase difference too big in case of X-Rays? If yes, then refractive index of the particle must be differentiating by larger amount than the surrounding.