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_4134993
_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         'I4 Pb, 2(C6 H12 F2 N) '
_chemical_formula_sum            'C12 H24 F4 I4 N2 Pb'
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_cell_length_a                   13.8350(14)
_cell_length_b                   9.9882(7)
_cell_length_c                   8.5383(8)
_cell_measurement_reflns_used    3005
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      29.5200
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_diffrn_measured_fraction_theta_full 0.997
_diffrn_measured_fraction_theta_max 0.997
_diffrn_measurement_device_type  'XtaLAB Synergy R, DW system, HyPix'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_unetI/netI     0.0731
_diffrn_reflns_Laue_measured_fraction_full 0.997
_diffrn_reflns_Laue_measured_fraction_max 0.997
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_diffrn_reflns_limit_h_min       -16
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_diffrn_reflns_limit_k_min       -11
_diffrn_reflns_limit_l_max       10
_diffrn_reflns_limit_l_min       -6
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_diffrn_reflns_point_group_measured_fraction_full 0.935
_diffrn_reflns_point_group_measured_fraction_max 0.935
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_diffrn_reflns_theta_max         25.242
_diffrn_reflns_theta_min         2.467
_diffrn_source                   'Rotating-anode X-ray tube'
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_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    2.873
_exptl_crystal_description       sheet
_exptl_crystal_F_000             880
_exptl_crystal_size_max          0.230
_exptl_crystal_size_mid          0.200
_exptl_crystal_size_min          0.180
_refine_diff_density_max         6.044
_refine_diff_density_min         -4.216
_refine_diff_density_rms         0.395
_refine_ls_abs_structure_details
;
 Classical Flack method preferred over Parsons because s.u. lower.
;
_refine_ls_abs_structure_Flack   0.193(13)
_refine_ls_extinction_method     none
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_refine_ls_restrained_S_all      1.079
_refine_ls_R_factor_all          0.0934
_refine_ls_R_factor_gt           0.0721
_refine_ls_shift/su_max          0.023
_refine_ls_shift/su_mean         0.004
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.1219P)^2^] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1923
_refine_ls_wR_factor_ref         0.2031
_reflns_Friedel_coverage         0.765
_reflns_Friedel_fraction_full    0.865
_reflns_Friedel_fraction_max     0.865
_reflns_number_gt                2861
_reflns_number_total             3778
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            ja0c03710_si_007.cif
_cod_data_source_block           p21_tw
_cod_depositor_comments
;Adding full bibliography for 4134988--4134996.cif.

 Adding full bibliography for 4134988--4134996.cif.
;
_cod_original_sg_symbol_H-M      'P 21'
_cod_database_code               4134993
_shelx_shelxl_version_number     2014/7
_shelx_estimated_absorpt_t_min   0.183
_shelx_estimated_absorpt_t_max   0.206
_shelx_res_checksum              45681
_shelx_hkl_checksum              79209