Ambiguous structure determination from powder data: four different structural models of 4,11-difluoroquinacridone with similar X-ray powder patterns, fit to the PDF, SSNMR and DFT-D
Schlesinger, Carina; Fitterer, Arnd; Buchsbaum, Christian; Habermehl, Stefan; Chierotti, Michele R.; Nervi, Carlo; Schmidt, Martin U.; IUCrJ 9 (2022) –; doi:10.1107/S2052252522004237

data_1566972
_publ_section_title
;
 Ambiguous structure determination from powder data: four different
 structural models of 4,11-difluoroquinacridone with similar X-ray powder
 patterns, fit to the PDF, SSNMR and DFT-D
;
_journal_coeditor_code           LT5047SUP1
_journal_issue                   4
_journal_name_full               IUCrJ
_journal_paper_doi               10.1107/S2052252522004237
_journal_volume                  9
_journal_year                    2022
_chemical_formula_moiety         'C20 H10 F2 N2 O2'
_chemical_formula_sum            'C20 H10 F2 N2 O2'
_chemical_formula_weight         348.3016
_chemical_name_common
;
4,11-Difluoro-quinacridone from Rietveld refinement
Remark: This is the correct structural model. 
The model which fits well to the powder data, 
fits well to the pair-distribution function,
has the lowest energy in lattice-energy minimisations, 
and agrees with solid-state NMR data.
Three wrong structural models are deposited in the CSD as well.
Further discussion see publication.
;
_chemical_name_systematic
'4,11-Difluoroquino[2,3-b]acridine-7,14(5H,12H)-dione, wrong structural model A'
_space_group_crystal_system      monoclinic
_space_group_IT_number           14
_space_group_name_Hall           '-P 2ybc'
_space_group_name_H-M_alt        'P 1 21/c 1'
_cell_angle_alpha                90
_cell_angle_beta                 102.504(12)
_cell_angle_gamma                90
_cell_formula_units_Z            2
_cell_length_a                   14.2172(15)
_cell_length_b                   3.76778(16)
_cell_length_c                   13.7038(13)
_cell_measurement_temperature    300
_cell_measurement_theta_max      79.9900
_cell_measurement_theta_min      4.50000
_cell_volume                     716.66(11)
_computing_cell_refinement       TOPAS-Academic
_computing_data_collection       '<i>WINX^POW^</i> (Stoe & Cie, 2004)'
_computing_data_reduction        '<i>WINX^POW^</i> (Stoe & Cie, 2004)'
_computing_molecular_graphics    '<i>Mercury</i> (Macrae <i>et al.</i>, 2008)'
_computing_structure_refinement  TOPAS-Academic
_computing_structure_solution    FIDEL
_diffrn_ambient_temperature      300
_diffrn_measurement_device_type  STOE-Stadi-P
_diffrn_radiation_monochromator  Ge(111)
_diffrn_radiation_type           'Cu K\a~1~'
_diffrn_radiation_wavelength     1.54056
_exptl_absorpt_coefficient_mu    1.048
_exptl_crystal_density_diffrn    1.614
_exptl_crystal_description       powder
_exptl_crystal_F_000             356
_pd_calc_method                  'Rietveld Refinement'
_pd_char_colour                  orange
_pd_char_particle_morphology     powder
_pd_meas_2theta_range_inc        0.010000
_pd_meas_2theta_range_max        79.9900
_pd_meas_2theta_range_min        2.00000
_pd_meas_number_of_points        7800
_pd_meas_scan_method             cont
_pd_proc_2theta_range_inc        0.010000
_pd_proc_2theta_range_max        79.9900
_pd_proc_2theta_range_min        4.50000
_pd_proc_ls_background_function  'Chebyshev function with 20 terms'
_pd_proc_ls_pref_orient_corr     none
_pd_proc_ls_profile_function     'fundamental parameters'
_pd_proc_ls_prof_R_factor        0.10919
_pd_proc_ls_prof_wR_expected     0.02320
_pd_proc_ls_prof_wR_factor       0.12239
_pd_proc_wavelength              1.54056
_pd_spec_mounting                'prepared between polymer films '
_pd_spec_mount_mode              transmission
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_all   5.275
_refine_ls_hydrogen_treatment    refxyz
_refine_ls_matrix_type           fullcycle
_refine_ls_number_constraints    0
_refine_ls_number_restraints     61
_refine_ls_R_factor_all          0.01504
_refine_ls_shift/su_max          0.001
_refine_ls_weighting_details     w=1/\s[Y~obs~]^2^
_refine_ls_weighting_scheme      sigma
_cod_data_source_file            lt5047.cif
_cod_data_source_block           DFQ_model_B_Rietveld
_cod_original_cell_volume        716.67(11)
_cod_original_sg_symbol_H-M      'P 21/c'
_cod_database_code               1566972