SAD intensity differences of Friedel pairs
These animations plot out the Bragg intensities of benzyl penicillin and seleno-benzyl penicillin as the photon energy is scanned across either the sulfur (from CXRO) or selenium K-edge (real data extracted by a Kramer-Kronig analysis of the Se-absorption spectrum in a small protein structure), respectively. The circle diameters are proportional to the square-root of the intensities, while the colour indicates the Bijvoet ratio from -2 (red), through 0 (white), to +2 (blue). The strongest breaking of Friedel’s law occurs at the maximum of f2 and the point of inflection of f1.
The program uses a function customcolormap.m, downloaded from MathWorks File Exchange, and for which I credit Victor Martinez-Cagigal.