Anisotropic lattice softening near the structural phase transition in the thermosalient crystal 1,2,4,5-tetrabromobenzene.
Zakharov, Boris A.; Michalchuk, Adam A. L.; Morrison, Carole A.; Boldyreva, Elena V.; Physical chemistry chemical physics : PCCP 20 (2018) 8523–8532; doi:10.1039/c7cp08609a

data_7230198
_publ_section_title
;
 Anisotropic lattice softening near the structural phase transition in the
 thermosalient crystal 1,2,4,5-tetrabromobenzene.
;
_journal_issue                   13
_journal_name_full               'Physical chemistry chemical physics : PCCP'
_journal_page_first              8523
_journal_page_last               8532
_journal_paper_doi               10.1039/c7cp08609a
_journal_volume                  20
_journal_year                    2018
_chemical_formula_moiety         'C6 H2 Br4'
_chemical_formula_sum            'C6 H2 Br4'
_chemical_formula_weight         393.72
_chemical_name_common            1,2,4,5-tetrabromobenzene
_chemical_name_systematic        1,2,4,5-tetrabromobenzene
_space_group_crystal_system      monoclinic
_space_group_IT_number           14
_space_group_name_Hall           '-P 2yn'
_space_group_name_H-M_alt        'P 1 21/n 1'
_symmetry_space_group_name_Hall  '-P 2yn'
_symmetry_space_group_name_H-M   'P 1 21/n 1'
_atom_sites_solution_hydrogens   geom
_audit_creation_method           SHELXL-2017/1
_audit_update_record
;
2017-10-10 deposited with the CCDC.
2018-02-26 downloaded from the CCDC.
;
_cell_angle_alpha                90
_cell_angle_beta                 100.168(4)
_cell_angle_gamma                90
_cell_formula_units_Z            2
_cell_length_a                   4.0108(2)
_cell_length_b                   10.6672(4)
_cell_length_c                   10.2811(4)
_cell_measurement_reflns_used    1749
_cell_measurement_temperature    283(2)
_cell_measurement_theta_max      28.2220
_cell_measurement_theta_min      4.0400
_cell_volume                     432.96(3)
_computing_cell_refinement
'CrysAlisPro 1.171.39.23a (Rigaku Oxford Diffraction, 2015)'
_computing_data_collection       'X-AREA (Stoe & Cie, 2013)'
_computing_data_reduction
'CrysAlisPro 1.171.39.23a (Rigaku Oxford Diffraction, 2015)'
_computing_molecular_graphics    'Mercury (Macrae et al., 2006)'
_computing_structure_refinement  'SHELXL-2017/1 (Sheldrick, 2017)'
_computing_structure_solution    'SHELXT (Sheldrick, 2015)'
_diffrn_ambient_temperature      283(2)
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_diffrn_measurement_device_type  'STOE IPDS II'
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_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0297
_diffrn_reflns_av_unetI/netI     0.0226
_diffrn_reflns_Laue_measured_fraction_full 1.000
_diffrn_reflns_Laue_measured_fraction_max 1.000
_diffrn_reflns_limit_h_max       4
_diffrn_reflns_limit_h_min       -5
_diffrn_reflns_limit_k_max       13
_diffrn_reflns_limit_k_min       -12
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_diffrn_reflns_number            2945
_diffrn_reflns_point_group_measured_fraction_full 1.000
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_diffrn_reflns_theta_max         26.354
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_diffrn_source                   'fine-focus sealed X-ray tube'
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_exptl_absorpt_process_details
;
CrysAlisPro 1.171.39.23a (Rigaku Oxford Diffraction, 2015)
Numerical absorption correction based on gaussian integration over
            a multifaceted crystal model
Empirical absorption correction using spherical harmonics,
 implemented in SCALE3 ABSPACK scaling algorithm.
;
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    3.020
_exptl_crystal_description       prism
_exptl_crystal_F_000             356
_exptl_crystal_size_max          0.720
_exptl_crystal_size_mid          0.110
_exptl_crystal_size_min          0.030
_refine_diff_density_max         0.521
_refine_diff_density_min         -0.542
_refine_diff_density_rms         0.142
_refine_ls_extinction_coef       0.023(2)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     'SHELXL-2017/1 (Sheldrick 2017)'
_refine_ls_goodness_of_fit_ref   1.042
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     47
_refine_ls_number_reflns         877
_refine_ls_number_restraints     0
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_refine_ls_R_factor_all          0.0355
_refine_ls_R_factor_gt           0.0295
_refine_ls_shift/su_max          0.001
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0541P)^2^] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0776
_refine_ls_wR_factor_ref         0.0805
_reflns_Friedel_coverage         0.000
_reflns_number_gt                762
_reflns_number_total             877
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            c7cp08609a2.cif
_cod_data_source_block           TBB_283K
_cod_depositor_comments
'Adding full bibliography for 7230191--7230198.cif.'
_cod_database_code               7230198
_shelx_shelxl_version_number     2017/1
_shelx_estimated_absorpt_t_min   0.026
_shelx_estimated_absorpt_t_max   0.607
_shelx_res_checksum              57871