Index

Macromolecular dictionary (mmCIF) version 2.0.09

_refine.overall_FOM_free_R_set

Definition:

   Average figure of merit of phases of reflections not included
   in the refinement.

   This value is derived from the likelihood function.

   FOM           = I_1(X)/I_0(X)

   I_0, I_1      = zero- and first-order modified Bessel functions
                   of the first kind
   X             = sigma_A |E_o| |E_c|/SIGMA
   E_o, E_c      = normalized observed and calculated structure
                   factors
   sigma_A       = <cos 2 pi s delta_x> SQRT(Sigma_P/Sigma_N)
                   estimated using maximum likelihood
   Sigma_P       = sum_{atoms in model} f^2
   Sigma_N       = sum_{atoms in crystal} f^2
   f             = form factor of atoms
   delta_x       = expected error
   SIGMA         = (sigma_{E;exp})^2 + epsilon [1-(sigma_A)^2]
   sigma_{E;exp} = uncertainties of normalized observed
                   structure factors
   epsilon       = multiplicity of the diffracting plane

   Ref: Murshudov, G. N., Vagin, A. A. & Dodson, E. J. (1997).
        Acta Cryst. D53, 240-255.

Type: float

Mandatory item: no

Category: refine