Confinement-Driven Ferroelectricity in a Two-Dimensional Hybrid Lead Iodide Perovskite.
Chen, Xiao-Gang; Song, Xian-Jiang; Zhang, Zhi-Xu; Zhang, Han-Yue; Pan, Qiang; Yao, Jie; You, Yu-Meng; Xiong, Ren-Gen; Journal of the American Chemical Society 142 (2020) 10212–10218; doi:10.1021/jacs.0c03710

data_4134996
_publ_section_title
;
 Confinement-Driven Ferroelectricity in a Two-Dimensional Hybrid Lead
 Iodide Perovskite.
;
_journal_issue                   22
_journal_name_full               'Journal of the American Chemical Society'
_journal_page_first              10212
_journal_page_last               10218
_journal_paper_doi               10.1021/jacs.0c03710
_journal_volume                  142
_journal_year                    2020
_chemical_formula_moiety
'4(I Pb0.25), 2(C F), 4(C0.50 N0.25), 4(C0.50)'
_chemical_formula_sum            'C6 F2 I4 N Pb'
_chemical_formula_weight         838.87
_space_group_crystal_system      tetragonal
_space_group_IT_number           121
_space_group_name_Hall           'I -4 2'
_space_group_name_H-M_alt        'I -4 2 m'
_audit_creation_method           SHELXL-2014/7
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            2
_cell_length_a                   6.6369(11)
_cell_length_b                   6.6369(11)
_cell_length_c                   27.272(6)
_cell_measurement_reflns_used    214
_cell_measurement_temperature    493(2)
_cell_measurement_theta_max      19.7400
_cell_measurement_theta_min      2.9700
_cell_volume                     1201.3(4)
_computing_structure_refinement  'SHELXL-2014/7 (Sheldrick, 2014)'
_diffrn_ambient_temperature      493(2)
_diffrn_measured_fraction_theta_full 0.995
_diffrn_measured_fraction_theta_max 0.864
_diffrn_measurement_device_type  'XtaLAB Synergy R, DW system, HyPix'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.2214
_diffrn_reflns_av_unetI/netI     0.3093
_diffrn_reflns_Laue_measured_fraction_full 0.995
_diffrn_reflns_Laue_measured_fraction_max 0.864
_diffrn_reflns_limit_h_max       9
_diffrn_reflns_limit_h_min       -6
_diffrn_reflns_limit_k_max       9
_diffrn_reflns_limit_k_min       -5
_diffrn_reflns_limit_l_max       16
_diffrn_reflns_limit_l_min       -37
_diffrn_reflns_number            1432
_diffrn_reflns_point_group_measured_fraction_full 0.961
_diffrn_reflns_point_group_measured_fraction_max 0.819
_diffrn_reflns_theta_full        25.242
_diffrn_reflns_theta_max         29.106
_diffrn_reflns_theta_min         2.988
_diffrn_source                   'Rotating-anode X-ray tube'
_exptl_absorpt_coefficient_mu    12.156
_exptl_absorpt_correction_T_max  0.038
_exptl_absorpt_correction_T_min  0.032
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details
;
CrysAlisPro 1.171.40.14e (Rigaku Oxford Diffraction, 2018)
Empirical absorption correction using spherical harmonics,
 implemented in SCALE3 ABSPACK scaling algorithm.
;
_exptl_crystal_colour            red
_exptl_crystal_density_diffrn    2.319
_exptl_crystal_description       sheeet
_exptl_crystal_F_000             710
_exptl_crystal_size_max          0.31
_exptl_crystal_size_mid          0.28
_exptl_crystal_size_min          0.27
_refine_diff_density_max         1.084
_refine_diff_density_min         -1.728
_refine_diff_density_rms         0.313
_refine_ls_abs_structure_details
;
 Flack x determined using 26 quotients [(I+)-(I-)]/[(I+)+(I-)]
 (Parsons, Flack and Wagner, Acta Cryst. B69 (2013) 249-259).
;
_refine_ls_abs_structure_Flack   1.0(6)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.174
_refine_ls_hydrogen_treatment    undef
_refine_ls_matrix_type           full
_refine_ls_number_parameters     44
_refine_ls_number_reflns         847
_refine_ls_number_restraints     53
_refine_ls_restrained_S_all      1.157
_refine_ls_R_factor_all          0.4250
_refine_ls_R_factor_gt           0.1909
_refine_ls_shift/su_max          0.093
_refine_ls_shift/su_mean         0.015
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.2000P)^2^] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.4486
_refine_ls_wR_factor_ref         0.5254
_reflns_Friedel_coverage         0.606
_reflns_Friedel_fraction_full    0.912
_reflns_Friedel_fraction_max     0.754
_reflns_number_gt                213
_reflns_number_total             847
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            ja0c03710_si_010.cif
_cod_data_source_block           I42M
_cod_depositor_comments
;Adding full bibliography for 4134988--4134996.cif.

 Adding full bibliography for 4134988--4134996.cif.
;
_cod_original_cell_volume        1201.3(5)
_cod_original_formula_sum        'C6 F2 I4 N Pb '
_cod_database_code               4134996
_shelx_shelxl_version_number     2014/7
_shelx_res_checksum              50477
_shelx_hkl_checksum              27051