Use of intensity quotients and differences in absolute structure refinement.
Parsons, Simon; Flack, Howard D.; Wagner, Trixie; Acta crystallographica Section B, Structural science, crystal engineering and materials 69 (2013) 249–259; doi:10.1107/S2052519213010014

data_2311267
_publ_section_title
;
 Use of intensity quotients and differences in absolute structure
 refinement.
;
_journal_issue                   'Pt 3'
_journal_name_full
'Acta crystallographica Section B, Structural science, crystal engineering and materials'
_journal_page_first              249
_journal_page_last               259
_journal_paper_doi               10.1107/S2052519213010014
_journal_volume                  69
_journal_year                    2013
_chemical_formula_sum            'C21 H22 N2'
_chemical_formula_weight         302.40
_space_group_crystal_system      orthorhombic
_space_group_IT_number           19
_space_group_name_Hall           'P 2ac 2ab'
_space_group_name_H-M_alt        'P 21 21 21'
_atom_sites_solution_hydrogens   difmap
_audit_creation_method           SHELXL-2012
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   6.0196(2)
_cell_length_b                   12.7041(4)
_cell_length_c                   21.6151(4)
_cell_measurement_temperature    100(2)
_cell_volume                     1652.98(8)
_computing_structure_refinement  'SHELXL-2012 (Sheldrick, 2012)'
_diffrn_ambient_temperature      100(2)
_diffrn_measured_fraction_theta_full 0.979
_diffrn_measured_fraction_theta_max 0.998
_diffrn_radiation_type           CuK\a
_diffrn_radiation_wavelength     1.54178
_diffrn_reflns_av_R_equivalents  0.0323
_diffrn_reflns_av_unetI/netI     0.0169
_diffrn_reflns_Laue_measured_fraction_full 0.979
_diffrn_reflns_Laue_measured_fraction_max 0.998
_diffrn_reflns_limit_h_max       7
_diffrn_reflns_limit_h_min       -7
_diffrn_reflns_limit_k_max       15
_diffrn_reflns_limit_k_min       -15
_diffrn_reflns_limit_l_max       25
_diffrn_reflns_limit_l_min       -25
_diffrn_reflns_number            30903
_diffrn_reflns_point_group_measured_fraction_full 0.978
_diffrn_reflns_point_group_measured_fraction_max 0.997
_diffrn_reflns_theta_full        67.679
_diffrn_reflns_theta_max         66.688
_diffrn_reflns_theta_min         4.036
_exptl_absorpt_coefficient_mu    0.544
_exptl_crystal_density_diffrn    1.215
_exptl_crystal_F_000             648
_exptl_crystal_size_max          0.180
_exptl_crystal_size_mid          0.130
_exptl_crystal_size_min          0.070
_refine_diff_density_max         0.144
_refine_diff_density_min         -0.160
_refine_diff_density_rms         0.033
_refine_ls_abs_structure_details
;
 Flack x determined using 1200 quotients [(I+)-(I-)]/[(I+)+(I-)]
 (Parsons and Flack (2004), Acta Cryst. A60, s61).
;
_refine_ls_abs_structure_Flack   0.04(6)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.082
_refine_ls_hydrogen_treatment    refall
_refine_ls_matrix_type           full
_refine_ls_number_parameters     296
_refine_ls_number_reflns         2920
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.082
_refine_ls_R_factor_all          0.0264
_refine_ls_R_factor_gt           0.0262
_refine_ls_shift/su_max          0.001
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
;
 w=1/[\s^2^(Fo^2^)+(0.0383P)^2^+0.2460P]
 where P=(Fo^2^+2Fc^2^)/3
;
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0663
_refine_ls_wR_factor_ref         0.0665
_reflns_Friedel_coverage         0.702
_reflns_Friedel_fraction_full    0.976
_reflns_Friedel_fraction_max     0.997
_reflns_number_gt                2892
_reflns_number_total             2920
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            TWA22A_B.cif
_cod_data_source_block           TWA22A_B
_cod_database_code               2311267
_shelx_estimated_absorpt_t_min   0.908
_shelx_estimated_absorpt_t_max   0.963
_shelxl_version_number           2012-9
_shelx_res_checksum              64466
_shelx_hkl_checksum              73753