I am not talking about crystallographic helices generated by screw axes that are trivial. More generally, non symmetric helices can be generated by the supramolecular packing (say for example through HB). In chiral crystal classes there are specific directions that are chiral and would enable helices, however I am looking for an automatic recognition of helices in actual structures. Do you know any algorithm or software that would enable recognizing such patterns?
Not sure if I understand the question, but in anisotropic crystals you can see the helical twist under polarized light the fiber becomes "segmented" as it twists in and out of phase with the cross polarizers
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Dear Michael, yes I know that however, we want to model phenomena like optical activity that requires calculation of the left and right rotated refraction index. In order to do so, one should recognize the helixes in the crystal structure and calculate the rotatory power taking into account the disposition of atomic polarizabilities in each direction of an helix. Now the problem is: given the structure of a molecular crystal, is there an easy algorithm to define the existence of a supramolecular helix? and how to recognize all the helices occurring in a crystal ? Many of them can be recognized visually, others are tricky because generated by crystallographic screw axis.
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