A variable-temperature study of a phase transition in barbituric acid dihydrate
Nichol, Gary S.; Clegg, William; Acta Crystallographica Section B 61 (2005) 464–472; doi:10.1107/S0108768105017258

data_2100272
_publ_section_title
;
 A variable-temperature study of a phase transition in barbituric acid
 dihydrate
;
_journal_coeditor_code           WS5026
_journal_issue                   4
_journal_name_full               'Acta Crystallographica Section B'
_journal_page_first              464
_journal_page_last               472
_journal_paper_doi               10.1107/S0108768105017258
_journal_volume                  61
_journal_year                    2005
_chemical_formula_moiety         'C4 H4 N2 O3, 2 H2 O'
_chemical_formula_sum            'C4 H8 N2 O5'
_chemical_formula_weight         164.12
_space_group_IT_number           14
_symmetry_cell_setting           monoclinic
_symmetry_space_group_name_Hall  '-P 2yn'
_symmetry_space_group_name_H-M   'P 1 21/n 1'
_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                 93.0680(16)
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   6.1270(5)
_cell_length_b                   12.7253(11)
_cell_length_c                   8.8633(8)
_cell_measurement_reflns_used    5619
_cell_measurement_temperature    170(2)
_cell_measurement_theta_max      28.25
_cell_measurement_theta_min      2.30
_cell_volume                     690.06(10)
_computing_cell_refinement       'Bruker SAINT'
_computing_data_collection       'Bruker SMART'
_computing_data_reduction        'Bruker SAINT'
_computing_molecular_graphics    'Bruker SHELXTL'
_computing_publication_material  'Bruker SHELXTL and local programs'
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_computing_structure_solution    'SHELXS-97 (Sheldrick, 1990)'
_diffrn_ambient_temperature      170(2)
_diffrn_measured_fraction_theta_full 0.999
_diffrn_measured_fraction_theta_max 0.963
_diffrn_measurement_device_type  'Bruker SMART 1K CCD diffractometer'
_diffrn_measurement_method       'thin-slice \w scans'
_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  0.0241
_diffrn_reflns_av_sigmaI/netI    0.0078
_diffrn_reflns_limit_h_max       8
_diffrn_reflns_limit_h_min       -8
_diffrn_reflns_limit_k_max       16
_diffrn_reflns_limit_k_min       -16
_diffrn_reflns_limit_l_max       11
_diffrn_reflns_limit_l_min       -11
_diffrn_reflns_number            9428
_diffrn_reflns_theta_full        26.00
_diffrn_reflns_theta_max         28.35
_diffrn_reflns_theta_min         2.80
_diffrn_standards_number         0
_exptl_absorpt_coefficient_mu    0.146
_exptl_absorpt_correction_T_max  0.9784
_exptl_absorpt_correction_T_min  0.8230
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'TWINABS; Sheldrick (2002)'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.580
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       block
_exptl_crystal_F_000             344
_exptl_crystal_size_max          0.53
_exptl_crystal_size_mid          0.42
_exptl_crystal_size_min          0.15
_refine_diff_density_max         0.300
_refine_diff_density_min         -0.327
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.161
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     120
_refine_ls_number_reflns         2124
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.161
_refine_ls_R_factor_all          0.0417
_refine_ls_R_factor_gt           0.0397
_refine_ls_shift/su_max          0.001
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0469P)^2^+0.1845P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1028
_refine_ls_wR_factor_ref         0.1045
_reflns_number_gt                2011
_reflns_number_total             2124
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            ws5026.cif
_cod_data_source_block           170
_cod_original_sg_symbol_H-M      'P 21/n'
_cod_database_code               2100272