Refinement Indicators

Structure refinement is done until the atoms stop shifting. The following indicators are used to provide information about the agreement between the measured intensities and those predicted by the modeled structure (from the Shelxl manual):

R_factor_all: R1 = Σ | |Fo| – |Fc| | / Σ |Fo|

R_factor_gt: R1 for F>4sigma

wR_factor_ref: weighted R-factor: wR2 = { Σ [ w(Fo2–Fc2)2 ] / Σ [ w(Fo2)2 ] }1/2 [check]

wR_factor_gt: weighted R-factor for F>4sigma [check]

goodness_of_fit_ref:GooF = S = { Σ [ w(Fo2–Fc2)2 ] / (n–p) }1/2, where n is the number of reflections and p is the number of parameters

Typical values for refinement depend on the crystal and the quality of the data. For high quality crystals of low-Z atoms, we may expect R-factors of 2-3%. 

Example values of refinement indicators from ic301543y_si_001.cif

_refine_ls_structure_factor_coef  Fsqd 

_refine_ls_matrix_type            full

_refine_ls_weighting_scheme       calc 

_refine_ls_weighting_details

 'calc w=1/[\s^2^(Fo^2^)+(0.0371P)^2^+3.5779P] where P=(Fo^2^+2Fc^2^)/3'

_atom_sites_solution_primary      direct

_atom_sites_solution_secondary    difmap

_atom_sites_solution_hydrogens    geom

_refine_ls_hydrogen_treatment     constr

_refine_ls_extinction_method      none

_refine_ls_extinction_coef        ?

_refine_ls_number_reflns          10683

_refine_ls_number_parameters      660

_refine_ls_number_restraints      76

_refine_ls_R_factor_all           0.0525

_refine_ls_R_factor_gt            0.0398

_refine_ls_wR_factor_ref          0.0995

_refine_ls_wR_factor_gt           0.0926

_refine_ls_goodness_of_fit_ref    1.015

_refine_ls_restrained_S_all       1.016

_refine_ls_shift/su_max           0.001

_refine_ls_shift/su_mean          0.000