Flack crystallographic analysis of absolute configuration

• Based on Bijvoet's heavy atom anomalous dispersion method
• Now possible for some good crystals of molecules without a heavy atom,
• Using a statistical analysis pioneered by Flack in 1983:
  • A Meaningful CIF Flack parameter:

    R1: 0.0284 with 0.0565
    wR2: 0.0513 with 0.1337
    Flack: 0.000(4) with 1.1016(4)
     _refine_ls_R_factor_obs+         0.0284
     _refine_ls_wR_factor_obs+        0.0513
     _refine_ls_abs_structure_Flack+  0.000(4)
     _refine_ls_R_factor_obs-         0.0565
     _refine_ls_wR_factor_obs-        0.1337
     _refine_ls_abs_structure_Flack-  1.016(4)
    

• Around 5-10 such determinations are done annually in this department.