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_2311265
_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            'C16 H18 N2'
_chemical_formula_weight         238.32
_space_group_crystal_system      trigonal
_space_group_IT_number           145
_space_group_name_Hall           'P 32'
_space_group_name_H-M_alt        'P 32'
_atom_sites_solution_hydrogens   mixed
_audit_creation_method           SHELXL-2012
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                120
_cell_formula_units_Z            3
_cell_length_a                   11.7721(4)
_cell_length_b                   11.7721(4)
_cell_length_c                   8.0824(3)
_cell_measurement_temperature    100(2)
_cell_volume                     970.02(6)
_computing_structure_refinement  'SHELXL-2012 (Sheldrick, 2012)'
_diffrn_ambient_temperature      100(2)
_diffrn_measured_fraction_theta_full 0.959
_diffrn_measured_fraction_theta_max 0.995
_diffrn_radiation_type           CuK\a
_diffrn_radiation_wavelength     1.54178
_diffrn_reflns_av_R_equivalents  0.0324
_diffrn_reflns_av_unetI/netI     0.0159
_diffrn_reflns_Laue_measured_fraction_full 0.959
_diffrn_reflns_Laue_measured_fraction_max 0.995
_diffrn_reflns_limit_h_max       14
_diffrn_reflns_limit_h_min       -13
_diffrn_reflns_limit_k_max       14
_diffrn_reflns_limit_k_min       -14
_diffrn_reflns_limit_l_max       8
_diffrn_reflns_limit_l_min       -9
_diffrn_reflns_number            30026
_diffrn_reflns_point_group_measured_fraction_full 0.928
_diffrn_reflns_point_group_measured_fraction_max 0.962
_diffrn_reflns_theta_full        67.679
_diffrn_reflns_theta_max         66.460
_diffrn_reflns_theta_min         4.337
_exptl_absorpt_coefficient_mu    0.556
_exptl_crystal_density_diffrn    1.224
_exptl_crystal_F_000             384
_exptl_crystal_size_max          0.460
_exptl_crystal_size_mid          0.120
_exptl_crystal_size_min          0.050
_refine_diff_density_max         0.151
_refine_diff_density_min         -0.127
_refine_diff_density_rms         0.032
_refine_ls_abs_structure_details
;
 Flack x determined using 1046 quotients [(I+)-(I-)]/[(I+)+(I-)]
 (Parsons and Flack (2004), Acta Cryst. A60, s61).
;
_refine_ls_abs_structure_Flack   0.18(8)
_refine_ls_extinction_coef       0.0164(17)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     SHELXL
_refine_ls_goodness_of_fit_ref   1.145
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     170
_refine_ls_number_reflns         2168
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      1.145
_refine_ls_R_factor_all          0.0283
_refine_ls_R_factor_gt           0.0283
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
;
 w=1/[\s^2^(Fo^2^)+(0.0275P)^2^+0.3075P]
 where P=(Fo^2^+2Fc^2^)/3
;
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0748
_refine_ls_wR_factor_ref         0.0748
_reflns_Friedel_coverage         0.935
_reflns_Friedel_fraction_full    0.896
_reflns_Friedel_fraction_max     0.930
_reflns_number_gt                2168
_reflns_number_total             2168
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            TWA16A_B.cif
_cod_data_source_block           TWA16A_B
_cod_original_cell_volume        970.02(8)
_cod_database_code               2311265
_shelx_estimated_absorpt_t_min   0.784
_shelx_estimated_absorpt_t_max   0.973
_shelxl_version_number           2012-9
_shelx_res_checksum              71762
_shelx_hkl_checksum              45852