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_2311260
_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 H29 N3'
_chemical_formula_weight         323.47
_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                   8.513(2)
_cell_length_b                   11.527(2)
_cell_length_c                   17.855(4)
_cell_measurement_temperature    100(2)
_cell_volume                     1752.1(6)
_computing_structure_refinement  'SHELXL-2012 (Sheldrick, 2012)'
_diffrn_ambient_temperature      100(2)
_diffrn_measured_fraction_theta_full 0.967
_diffrn_measured_fraction_theta_max 0.989
_diffrn_radiation_type           CuK\a
_diffrn_radiation_wavelength     1.54178
_diffrn_reflns_av_R_equivalents  0.0326
_diffrn_reflns_av_unetI/netI     0.0129
_diffrn_reflns_Laue_measured_fraction_full 0.967
_diffrn_reflns_Laue_measured_fraction_max 0.989
_diffrn_reflns_limit_h_max       10
_diffrn_reflns_limit_h_min       -10
_diffrn_reflns_limit_k_max       13
_diffrn_reflns_limit_k_min       -13
_diffrn_reflns_limit_l_max       20
_diffrn_reflns_limit_l_min       -18
_diffrn_reflns_number            53779
_diffrn_reflns_point_group_measured_fraction_full 0.967
_diffrn_reflns_point_group_measured_fraction_max 0.991
_diffrn_reflns_theta_full        67.679
_diffrn_reflns_theta_max         66.590
_diffrn_reflns_theta_min         4.566
_exptl_absorpt_coefficient_mu    0.554
_exptl_crystal_density_diffrn    1.226
_exptl_crystal_F_000             704
_exptl_crystal_size_max          0.790
_exptl_crystal_size_mid          0.300
_exptl_crystal_size_min          0.300
_refine_diff_density_max         0.158
_refine_diff_density_min         -0.130
_refine_diff_density_rms         0.029
_refine_ls_abs_structure_details
;
 Flack x determined using 1295 quotients [(I+)-(I-)]/[(I+)+(I-)]
 (Parsons and Flack (2004), Acta Cryst. A60, s61).
;
_refine_ls_abs_structure_Flack   0.01(4)
_refine_ls_extinction_coef       0.0108(9)
_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   1.105
_refine_ls_hydrogen_treatment    refall
_refine_ls_matrix_type           full
_refine_ls_number_parameters     334
_refine_ls_number_reflns         3071
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.105
_refine_ls_R_factor_all          0.0247
_refine_ls_R_factor_gt           0.0247
_refine_ls_shift/su_max          0.004
_refine_ls_shift/su_mean         0.001
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
;
 w=1/[\s^2^(Fo^2^)+(0.0363P)^2^+0.2813P]
 where P=(Fo^2^+2Fc^2^)/3
;
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0647
_refine_ls_wR_factor_ref         0.0647
_reflns_Friedel_coverage         0.732
_reflns_Friedel_fraction_full    0.967
_reflns_Friedel_fraction_max     0.994
_reflns_number_gt                3069
_reflns_number_total             3071
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            TWA21A_B.cif
_cod_data_source_block           TWA21A_B
_cod_database_code               2311260
_shelx_estimated_absorpt_t_min   0.669
_shelx_estimated_absorpt_t_max   0.851
_shelxl_version_number           2012-9
_shelx_res_checksum              78994
_shelx_hkl_checksum              9270