M3-x(NH4)xCrO8 (M = Na, K, Rb, Cs): A New Family of Cr5±Based Magnetic Ferroelectrics
Raghabendra Samantaray; Ronald J. Clark; Eun S. Choi; Haidong Zhou; Naresh S. Dalal; Journal of the American Chemical Society 133 (2011) 3792–3795; doi:10.1021/ja1117683

data_4105793
_publ_section_title
;
 M3-x(NH4)xCrO8 (M = Na, K, Rb, Cs): A New Family of Cr5+-Based Magnetic
 Ferroelectrics
;
_journal_name_full               'Journal of the American Chemical Society'
_journal_page_first              3792
_journal_page_last               3795
_journal_paper_doi               10.1021/ja1117683
_journal_volume                  133
_journal_year                    2011
_chemical_formula_sum            'Cr H8 N2 O8 Rb'
_chemical_formula_weight         301.55
_chemical_name_systematic
; 
 ? 
;
_space_group_IT_number           121
_symmetry_cell_setting           tetragonal
_symmetry_space_group_name_Hall  'I -4 2'
_symmetry_space_group_name_H-M   'I -4 2 m'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-97
_cell_angle_alpha                90.00
_cell_angle_beta                 90.00
_cell_angle_gamma                90.00
_cell_formula_units_Z            2
_cell_length_a                   6.9862(3)
_cell_length_b                   6.9862(3)
_cell_length_c                   7.9044(6)
_cell_measurement_temperature    193(2)
_cell_volume                     385.79(4)
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 1990)'
_diffrn_ambient_temperature      193(2)
_diffrn_measured_fraction_theta_full 1.000
_diffrn_measured_fraction_theta_max 1.000
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0250
_diffrn_reflns_av_sigmaI/netI    0.0157
_diffrn_reflns_limit_h_max       9
_diffrn_reflns_limit_h_min       -9
_diffrn_reflns_limit_k_max       9
_diffrn_reflns_limit_k_min       -9
_diffrn_reflns_limit_l_max       10
_diffrn_reflns_limit_l_min       -10
_diffrn_reflns_number            2625
_diffrn_reflns_theta_full        28.23
_diffrn_reflns_theta_max         28.23
_diffrn_reflns_theta_min         3.89
_exptl_absorpt_coefficient_mu    7.768
_exptl_crystal_density_diffrn    2.596
_exptl_crystal_F_000             294
_refine_diff_density_max         0.342
_refine_diff_density_min         -0.625
_refine_diff_density_rms         0.145
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   0.07(2)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   0.969
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     26
_refine_ls_number_reflns         271
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      0.967
_refine_ls_R_factor_all          0.0242
_refine_ls_R_factor_gt           0.0242
_refine_ls_shift/su_max          0.808
_refine_ls_shift/su_mean         0.142
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0400P)^2^+2.3495P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0640
_refine_ls_wR_factor_ref         0.0641
_reflns_number_gt                269
_reflns_number_total             271
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            ja1117683_si_004.cif
_cod_data_source_block           dal141
_cod_original_formula_sum        'H8 Cr N2 O8 Rb'
_cod_database_code               4105793