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