Hydrogen migration in oxalic acid di-hydrate at high pressure?
Casati, Nicola; Macchi, Piero; Sironi, Angelo; Chemical communications (Cambridge, England) 34 (2009) 2679–2681; doi:10.1039/b823458b

data_7104409
_publ_section_title
;
 Hydrogen migration in oxalic acid di-hydrate at high pressure?
;
_journal_issue                   19
_journal_name_full               'Chemical communications (Cambridge, England)'
_journal_page_first              2679
_journal_page_last               2681
_journal_paper_doi               10.1039/b823458b
_journal_volume                  34
_journal_year                    2009
_chemical_formula_sum            'C H3 O3'
_chemical_formula_weight         63.03
_chemical_name_common            'oxalic acid dihydrate'
_chemical_name_systematic
;
oxalic acid dihydrate
;
_space_group_IT_number           14
_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_date             2008-09-26T13:40:15-00:00
_audit_creation_method           'WinGX routine CIF_UPDATE'
_cell_angle_alpha                90.00
_cell_angle_beta                 106.01(4)
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   5.8093(7)
_cell_length_b                   3.1657(9)
_cell_length_c                   11.676(4)
_cell_measurement_reflns_used    985
_cell_measurement_temperature    295(2)
_cell_measurement_theta_max      23.1
_cell_measurement_theta_min      4.5
_cell_volume                     206.39(10)
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_diffrn_ambient_environment      'collected in a diamond anvil cell'
_diffrn_ambient_pressure         3600000
_diffrn_ambient_temperature      295(2)
_diffrn_measured_fraction_theta_full 0.545
_diffrn_measured_fraction_theta_max 0.545
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_source         'fine-focus sealed tube'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71069
_diffrn_reflns_av_R_equivalents  0.0654
_diffrn_reflns_av_sigmaI/netI    0.0352
_diffrn_reflns_limit_h_max       6
_diffrn_reflns_limit_h_min       -6
_diffrn_reflns_limit_k_max       3
_diffrn_reflns_limit_k_min       -3
_diffrn_reflns_limit_l_max       10
_diffrn_reflns_limit_l_min       -10
_diffrn_reflns_number            2220
_diffrn_reflns_theta_full        25.03
_diffrn_reflns_theta_max         25.03
_diffrn_reflns_theta_min         4.50
_exptl_absorpt_coefficient_mu    0.215
_exptl_absorpt_correction_T_max  1.0
_exptl_absorpt_correction_T_min  0.84
_exptl_absorpt_correction_type   empirical
_exptl_absorpt_process_details
;
DAC absorption corrected with Absorb 6.0 (gaussian)
(R.J. Angel, J. Appl. Cryst. 2004, 37(3), 486)
Crystal absorption corrected with SADABS (empirical)
Area-Detector Absorption Correction,
(Siemens Industrial Automation, Inc.: Madison, WI, 1996)
;
_exptl_crystal_density_diffrn    2.029
_exptl_crystal_density_method    'not measured'
_exptl_crystal_F_000             132
_exptl_crystal_preparation       'mounted in a diamond-anvil cell '
_refine_diff_density_max         0.162
_refine_diff_density_min         -0.196
_refine_diff_density_rms         0.053
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.140
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     43
_refine_ls_number_reflns         198
_refine_ls_number_restraints     2
_refine_ls_restrained_S_all      1.133
_refine_ls_R_factor_all          0.0479
_refine_ls_R_factor_gt           0.0387
_refine_ls_shift/su_max          0.000
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0700P)^2^+0.0154P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.0928
_refine_ls_wR_factor_ref         0.0984
_reflns_number_gt                170
_reflns_number_total             198
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            B823458B.txt
_cod_data_source_block           oxhh52u
_cod_original_sg_symbol_H-M      'P 21/n'
_cod_database_code               7104409