Antiferroelectric Phase Transition in a Proton-Transfer Salt of Squaric Acid and 2,3-Dimethylpyrazine.
Lengyel, Jeff; Wang, Xiaoping; Choi, Eun Sang; Besara, Tiglet; Schönemann, Rico; Ramakrishna, Sanath Kumar; Holleman, Jade; Blockmon, Avery L.; Hughey, Kendall D.; Liu, Tianhan; Hudis, Jacob; Beery, Drake; Balicas, Luis; McGill, Stephen A.; Hanson, Kenneth; Musfeldt, Janice L.; Siegrist, Theo; Dalal, Naresh S.; Shatruk, Michael; Journal of the American Chemical Society 141 (2019) 16279–16287; doi:10.1021/jacs.9b04473

data_4127700
_publ_section_title
;
 Antiferroelectric Phase Transition in a Proton-Transfer Salt of Squaric
 Acid and 2,3-Dimethylpyrazine.
;
_journal_issue                   41
_journal_name_full               'Journal of the American Chemical Society'
_journal_page_first              16279
_journal_page_last               16287
_journal_paper_doi               10.1021/jacs.9b04473
_journal_volume                  141
_journal_year                    2019
_chemical_formula_moiety         'C4 H3 O5, C6 H9 N2'
_chemical_formula_sum            'C10 H12 N2 O5'
_chemical_formula_weight         240.22
_space_group_crystal_system      triclinic
_space_group_IT_number           2
_space_group_name_Hall           '-P 1'
_space_group_name_H-M_alt        'P -1'
_symmetry_space_group_name_Hall  '-P 1'
_symmetry_space_group_name_H-M   'P -1'
_atom_sites_solution_hydrogens   difmap
_audit_creation_date             2018-11-23
_audit_creation_method
;
Olex2 1.2
(compiled 2018.05.29 svn.r3508 for OlexSys, GUI svn.r5506)
;
_cell_angle_alpha                76.398(5)
_cell_angle_beta                 89.550(6)
_cell_angle_gamma                80.515(6)
_cell_formula_units_Z            2
_cell_length_a                   6.721(4)
_cell_length_b                   7.967(4)
_cell_length_c                   10.750(6)
_cell_measurement_reflns_used    17498
_cell_measurement_temperature    230
_cell_measurement_theta_max      78.553
_cell_measurement_theta_min      7.461
_cell_volume                     551.5(5)
_computing_cell_refinement       Mantidplot
_computing_data_collection       'SNS PyDas'
_computing_data_reduction        Mantidplot
_computing_molecular_graphics    'Olex2 (Dolomanov et al., 2009)'
_computing_publication_material  'Olex2 (Dolomanov et al., 2009)'
_computing_structure_refinement  'ShelXL (Sheldrick, 2015)'
_diffrn_ambient_temperature      230
_diffrn_measured_fraction_theta_full 0.755
_diffrn_measured_fraction_theta_max 0.307
_diffrn_measurement_device_type  TOPAZ
_diffrn_measurement_method       'time-of-flight Laue'
_diffrn_radiation_type           neutrons
_diffrn_radiation_wavelength     0.6
_diffrn_radiation_wavelength_details 'Based on neutron time of flight'
_diffrn_reflns_av_R_equivalents  0.1138
_diffrn_reflns_av_unetI/netI     0.0947
_diffrn_reflns_Laue_measured_fraction_full 0.755
_diffrn_reflns_Laue_measured_fraction_max 0.307
_diffrn_reflns_limit_h_max       11
_diffrn_reflns_limit_h_min       -11
_diffrn_reflns_limit_k_max       15
_diffrn_reflns_limit_k_min       -12
_diffrn_reflns_limit_l_max       19
_diffrn_reflns_limit_l_min       -19
_diffrn_reflns_number            5223
_diffrn_reflns_point_group_measured_fraction_full 0.755
_diffrn_reflns_point_group_measured_fraction_max 0.307
_diffrn_reflns_theta_full        21.100
_diffrn_reflns_theta_max         78.550
_diffrn_reflns_theta_min         7.464
_diffrn_source                   'The ORNL Spallation Neutron Scource'
_exptl_absorpt_coefficient_mu    0.2175
_exptl_absorpt_correction_T_max  0.7257
_exptl_absorpt_correction_T_min  0.4307
_exptl_absorpt_correction_type   sphere
_exptl_absorpt_process_details
;
C. W. Dwiggins, Jr., Acta Cryst. A31, 395 (1975).
;
_exptl_crystal_colour            'clear yellow'
_exptl_crystal_colour_lustre     clear
_exptl_crystal_colour_primary    yellow
_exptl_crystal_density_diffrn    1.446
_exptl_crystal_description       block
_exptl_crystal_F_000             252
_exptl_crystal_size_max          3.6
_exptl_crystal_size_mid          1.35
_exptl_crystal_size_min          0.85
_refine_diff_density_max         1.017
_refine_diff_density_min         -0.884
_refine_diff_density_rms         0.208
_refine_ls_extinction_coef       0.057(10)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method     'SHELXL-2014/7 (Sheldrick 2014'
_refine_ls_goodness_of_fit_ref   1.169
_refine_ls_hydrogen_treatment    refall
_refine_ls_matrix_type           full
_refine_ls_number_parameters     297
_refine_ls_number_reflns         2796
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.169
_refine_ls_R_factor_all          0.0788
_refine_ls_R_factor_gt           0.0780
_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^)+(0.0792P)^2^+1.9533P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1789
_refine_ls_wR_factor_ref         0.1793
_reflns_Friedel_coverage         0.000
_reflns_number_gt                2785
_reflns_number_total             2796
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            ja9b04473_si_005.cif
_cod_data_source_block           230k
_cod_database_code               4127700
_shelx_shelxl_version_number     2014/7
_exptl_absorpt_special_details
;
Neutron linear absorption coefficient is wavelength dependent.
For each peak, the absorption coefficient mu is calculated as:
          mu = 1.2957 + 1.5810/1.7982 * wavelength  [cm^-1^]
where 
 1.2957 cm^-1 is the absorption coefficient for total scattering;
 1.5810 cm^-1 is the absorption coefficient for true absorption at 1.7982 A.
 
The value of 0.2175 (mm^-1^) shown in _exptl_absorpt_coefficient_mu 
is the sample absorption coefficient for neutron wavelength at 1.0 \%A.
;
_diffrn_reflns_min_d_angs        0.500
_olex2_refinement_description
;
1. Others
 Sof(H8BA)=Sof(H8BB)=Sof(H8BC)=1-FVAR(1)
 Sof(H8AA)=Sof(H8AB)=Sof(H8AC)=FVAR(1)
 Fixed Sof: H5B(0.5)
;
_olex2_submission_special_instructions 'No special instructions were received'