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Figure 6
The figure shows a schematic [Mathematical equation11] diffraction pattern for the MX rock salt structure. If the scattering factors of M and X differ, the open circles represent weak diffraction spots, as outlined in detail in Fig. 5[link] for the 111 reflection of NaCl boxed here. However, if the two scattering factors are of the same magnitude, which is the case for K+ and Cl− in potassium chloride (both ions carry 18 shell electrons), the scattering from each ion is just cancelled out by the scattering of the counter-ion. As a result, the intensities of all reflections with open circles are zero. The latter is the case for reflections in this pattern where all hkl have odd indices. However, the two ions are always in phase and add their scattering power to yield strong reflections when all hkl are even.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 82| Part 2| February 2026| Pages 235-243
https://doi.org/10.1107/S2056989026000745
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