Figure 2
(a), (b) Two-beam calculations of the wavefield modulation for the centrosymmetric model, space group (No. 225), with the Bragg condition fulfilled for (a) the reflection and (b) the 111 reflection. (c), (d) Similarly for the non-centrosymmetric model, space group (No. 216). In the analytical calculations for both the centrosymmetric and non-centrosymmetric models, the origin is chosen at the same position within the figure (vertical dotted line). The origin for both models is at the position resulting in a real and positive structure factor for the 111 reflection (and thus also for the reflection). This origin is in the Sn plane in the centrosymmetric model and the crystal had to be shifted by 25°/360° parts on the repetition unit for the non-centrosymmetric model. |