Evolution of the α-BaMg(CO<sub>3</sub>)<sub>2</sub> low-temperature superstructure and the tricritical nature of its α-β phase transition.
Ende, Martin; Effenberger, Herta; Miletich, Ronald; Acta crystallographica Section B, Structural science, crystal engineering and materials 73 (2017) 827–835; doi:10.1107/S2052520617009295

data_2311757
_publ_section_title
;
 Evolution of the \a-BaMg(CO<sub>3</sub>)<sub>2</sub> low-temperature
 superstructure and the tricritical nature of its \a-\b phase transition.
;
_journal_issue                   'Pt 5'
_journal_name_full
'Acta crystallographica Section B, Structural science, crystal engineering and materials'
_journal_page_first              827
_journal_page_last               835
_journal_paper_doi               10.1107/S2052520617009295
_journal_volume                  73
_journal_year                    2017
_chemical_formula_sum            'C6 Ba3 Mg3 O18'
_chemical_formula_weight         845.01
_space_group_crystal_system      trigonal
_space_group_IT_number           166
_space_group_name_Hall           '-R 3 2"'
_space_group_name_H-M_alt        'R -3 m :H'
_audit_creation_method           SHELXL-2014/7
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                120
_cell_formula_units_Z            1
_cell_length_a                   5.0224(2)
_cell_length_b                   5.0224(2)
_cell_length_c                   16.8222(8)
_cell_measurement_reflns_used    5148
_cell_measurement_temperature    420(2)
_cell_measurement_theta_max      45
_cell_measurement_theta_min      1.5
_cell_volume                     367.48(3)
_computing_structure_refinement  'SHELXL-2014/7 (Sheldrick, 2014)'
_diffrn_ambient_temperature      420(2)
_diffrn_measured_fraction_theta_full 0.990
_diffrn_measured_fraction_theta_max 0.993
_diffrn_measurement_device_type  StoeStadiVari
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0291
_diffrn_reflns_av_unetI/netI     0.0126
_diffrn_reflns_Laue_measured_fraction_full 0.990
_diffrn_reflns_Laue_measured_fraction_max 0.993
_diffrn_reflns_limit_h_max       10
_diffrn_reflns_limit_h_min       -9
_diffrn_reflns_limit_k_max       9
_diffrn_reflns_limit_k_min       -10
_diffrn_reflns_limit_l_max       17
_diffrn_reflns_limit_l_min       -33
_diffrn_reflns_number            5148
_diffrn_reflns_point_group_measured_fraction_full 0.990
_diffrn_reflns_point_group_measured_fraction_max 0.993
_diffrn_reflns_theta_full        25.242
_diffrn_reflns_theta_max         45.525
_diffrn_reflns_theta_min         3.634
_exptl_absorpt_coefficient_mu    8.191
_exptl_absorpt_correction_T_max  0.8
_exptl_absorpt_correction_T_min  0.7
_exptl_absorpt_correction_type   numerical
_exptl_absorpt_process_details   '(Stoe & Cie GmbH 2016)'
_exptl_crystal_density_diffrn    3.818
_exptl_crystal_description       prismatic
_exptl_crystal_F_000             384
_exptl_crystal_size_max          0.060
_exptl_crystal_size_mid          0.030
_exptl_crystal_size_min          0.030
_refine_diff_density_max         1.045
_refine_diff_density_min         -0.720
_refine_diff_density_rms         0.126
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.179
_refine_ls_hydrogen_treatment    undef
_refine_ls_matrix_type           full
_refine_ls_number_parameters     14
_refine_ls_number_reflns         428
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.179
_refine_ls_R_factor_all          0.0132
_refine_ls_R_factor_gt           0.0132
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0095P)^2^+0.7440P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0306
_refine_ls_wR_factor_ref         0.0306
_reflns_Friedel_coverage         0.000
_reflns_number_gt                428
_reflns_number_total             428
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            xk5041sup1.cif
_cod_data_source_block           norse_420
_cod_original_sg_symbol_H-M      'R -3 m'
_cod_database_code               2311757
_shelx_shelxl_version_number     2014/7
_shelx_estimated_absorpt_t_min   0.639
_shelx_estimated_absorpt_t_max   0.791
_shelx_res_checksum              61598
_shelx_hkl_checksum              21119