[phenixbb] Scattering from riding hydrogens?
dcekiert at scripps.edu
Mon Nov 14 14:21:17 PST 2011
I have a question regarding two parameters and how they affect riding hydrogens.
contribute_to_f_calc = True
high_resolution_limit_to_include_scattering_from_h = 1.6
At lower resolution, setting contribute_to_f_calc = false is frequently helpful when using riding hydrogens and has been discussed before. But what is high_resolution_limit_to_include_scattering_from_h = 1.6 doing? If scattering from hydrogens is only included at higher than 1.6A resolution, it would seem like contribute_to_f_calc = True/False would not have any effect at say, 3.5A, but comparing identical refinement runs with contribute_to_f_calc = True or contribute_to_f_calc = False clearly gives different results. Can hydrogens contribute to Fcalc in a way aside from their scattering, or is their contribution accounted for independent of the position of the riding hydrogen (e.g., additional scattering term added to the associated heavy atom)? I think I am misunderstanding what these two parameters are doing and would appreciate some clarification.
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