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Core CIF Dictionary version 2.3




Category: refine

Data type: numb (with optional s.u. in parentheses)

Related item: '_refine_ls_goodness_of_fit_obs'
Related function: alternate

Enumeration range: 0.0 -> infinity


   The least-squares goodness-of-fit parameter S for
   significantly intense reflections, (see
   _reflns_threshold_expression), after the final cycle of
   refinement. Ideally, account should be taken of parameters
   restrained in the least squares. See also
   _refine_ls_restrained_S_ definitions.

       {  sum { w [ Y(obs) - Y(calc) ]^2^ }  }^1/2^
   S = { ----------------------------------- }
       {            Nref - Nparam            }

   Y(obs)  = the observed coefficients
             (see _refine_ls_structure_factor_coef)
   Y(calc) = the calculated coefficients
             (see _refine_ls_structure_factor_coef)
   w       = the least-squares reflection weight
   u       = standard uncertainty

   Nref   = the number of reflections used in the refinement
   Nparam = the number of refined parameters

   and the sum is taken over the specified reflections

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