Determination of structural chirality of berlinite and quartz using resonant x-ray diffraction with circularly polarized x-rays

Many proteins, sugars, and pharmaceuticals crystallize into two forms that are mirror images of each other (enantiomers) such as our right and left hands (chiral). Berlinite (AlPO₄) and low quartz (SiO₂) have enantiomers belonging to a space-group pair, P3₁21 (right-handed screw) and P3₂21 (left-handed screw). We use circularly polarized resonant x-ray diffraction to study structural chirality. Our results demonstrate that positive and negative circularly polarized x-rays at the resonant energy of berlinite ( Al1s edge) and low quartz ( Si1s edge) can distinguish the absolute structure (right or left-handed screw) of an enantiomer. The advantage of our method is that the measurement of only one space-group forbidden reflection is enough to determine the chirality. This method is applicable to chiral motifs that occur in biomolecules, liquid crystals, ferroelectrics and antiferroelectrics, multiferroics, etc.