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Item _refine.overall_SU_R_Cruickshank_DPI

Description

              The overall standard uncertainty (estimated standard deviation)
               of the displacement 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. J. (1999). Acta Cryst. D55, 583-601.

                    Murshudov, G. N. & Dodson,
                    E. J. (1997). Simplified error estimation a la
                    Cruickshank in macromolecular crystallography.
                    CCP4 Newsletter on Protein Crystallography, No. 33,
                    January 1997, pp. 31-39.
                   http://www.ccp4.ac.uk/newsletters/newsletter33/murshudov.html

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