Item _refine.overall_SU_R_free

Description

              The overall standard uncertainty (e.s.d.) of the thermal
               parameters based on the free R value.

               The overall standard uncertainty gives an idea of the
               uncertainty in the B values of averagely defined atoms
               (atoms with B values equal to the average B value).

                                    N_a
               (sigma_B)^2  = 0.65 ----- (R_free)^2 (D_min)^2 C^(-2/3)
                                    N_o

               N_a    = number of atoms
               N_o    = number of reflections included in refinement
               N_p    = number of refined parameters
               R_free = conventional free crystallographic R-value calculated
                        using reflections not included in refinement
               D_min  = maximum resolution
               C      = completeness of data

               Ref: Cruickshank, D. W. (1997). "Refinement of macromolecular
                    structures". Proc. CCP4 study weekend.

                    "Simplified error estimation a la Cruickshank in
                    macromolecular crystallography", Murshudov G. N. &
                    Dodson E. J. (1997). CCP4 Newsletter, no. 33.
                    http://www.dl.ac.uk/CCP/CCP4/newsletter33/

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