Item _refine.overall_SU_R_Cruickshank_DPI

Description

              The overall standard uncertainty (e.s.d.) of the thermal
               parameters based on the crystallographic R value, expressed
               in a formalism known as the dispersion precision indicator
               (DPI).

               The overall standard uncertainty (sigma~B~) 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_value)^2 (D_min)^2 C^(-2/3)
                                   (N_o-N_p)


               N_a      = number of atoms
               N_o      = number of reflections included in refinement
               N_p      = number of refined parameters
               R_value  = conventional crystallographic R-value
               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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