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#                                                                            #
# This CIF contains the data in a paper accepted for publication in Acta     #
# Crystallographica Section A. It has been peer reviewed under the auspices  #
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data_urea
_journal_date_recd_electronic     2004-02-28
_journal_date_accepted     2004-06-21
_journal_name_full     'Acta Crystallographica, Section A'
_journal_year     2004
_journal_volume     60
_journal_issue      5
_journal_page_first     371
_journal_page_last     381
_journal_paper_category     FA
loop_
    _publ_contact_author_name
    _publ_contact_author_address
    _publ_contact_author_email
    'Henrik Birkedal'
;
Department of Chemistry and Biochemistry
University of California, Santa Barbara
CA 93106-9510, USA
;
 'hbirkedal@chem.ucsb.edu'
    'Dennis Madsen'
;
Novo Nordisk A/S,
Department of Scientific Computing
Novo Nordisk Park, A2P
DK-2760 Mål\ov
Denmark
;
 'dnnm@novonordisk.com'
_publ_section_title
;
The Charge Density of Urea from Synchrotron Diffraction Data
;
loop_
    _publ_author_name
    _publ_author_footnote
    _publ_author_address
    'Henrik Birkedal'
;
Department of Chemistry and Biochemistry
University of California, Santa Barbara
CA 93106-9510, USA
;
;
Laboratory of Crystallography
Swiss Federal Institute of Technology
BSP
CH-1015 Lausanne, Switzerland
;
    'Dennis Madsen'
;
Novo Nordisk A/S,
Department of Scientific Computing
Novo Nordisk Park, A2P
DK-2760 Mål\ov
Denmark
;
;
European Synchrotron Radiation Facility
Rue Jules Horowitz 6
BP 220
F-38043 Grenoble Cedex, France
;
    'Ragnvald H. Mathiesen'
;
SINTEF
Applied Physics Department
N-7465 Trondheim, Norway
;
;
Institutt for Fysikk
NTNU
N-7491 Trondheim, Norway
;
    'Kenneth D. Knudsen'
;
Institute for Energy Technology
Physics Department
N-2027 Kjeller, Norway
;
;
Swiss-Norwegian Beam Lines at ESRF
Rue Jules Horowitz 6
BP 220
F-38043 Grenoble Cedex, France
;
    'Hans-Peter Weber'
;
;
;
Laboratory of Crystallography
Swiss Federal Institute of Technology
BSP
CH-1015 Lausanne, Switzerland
and
Swiss-Norwegian Beam Lines at ESRF
Rue Jules Horowitz 6
BP 220
F-38043 Grenoble Cedex, France
;
    'Philip Pattison'
;
;
;
Laboratory of Crystallography
Swiss Federal Institute of Technology
BSP
CH-1015 Lausanne, Switzerland
and
Swiss-Norwegian Beam Lines at ESRF
Rue Jules Horowitz 6
BP 220
F-38043 Grenoble Cedex, France
;
    'Dieter Schwarzenbach'
;
;
;
Laboratory of Crystallography
Swiss Federal Institute of Technology
BSP
CH-1015 Lausanne, Switzerland
;
data_I
_journal_date_recd_electronic     2004-02-28
_journal_date_accepted     2004-06-21
_journal_name_full     'Acta Crystallographica, Section A'
_journal_year     2004
_journal_volume     60
_journal_issue      5
_journal_page_first     371
_journal_page_last     381
_journal_paper_category     FA
_chemical_name_systematic
;
 ?
;
_chemical_name_common     'urea'
_chemical_formula_moiety     'C H4 N2 O'
_chemical_formula_sum     'C H4 N2 O'
_chemical_formula_weight     60.06
_chemical_melting_point     ?
_symmetry_cell_setting     tetragonal
_symmetry_space_group_name_H-M     'P -4 21 m'
_symmetry_space_group_name_Hall     'P -4 2ab'
loop_
    _symmetry_equiv_pos_as_xyz
    'x, y, z'
    '-x, -y, z'
    'y, -x, -z'
    '-y, x, -z'
    '-x+1/2, y+1/2, -z'
    'x+1/2, -y+1/2, -z'
    '-y+1/2, -x+1/2, z'
    'y+1/2, x+1/2, z'
_cell_length_a     5.5780(6)
_cell_length_b     5.5780(6)
_cell_length_c     4.6860(7)
_cell_angle_alpha     90.00
_cell_angle_beta     90.00
_cell_angle_gamma     90.00
_cell_volume     145.80(3)
_cell_formula_units_Z     2
_cell_measurement_reflns_used     17
_cell_measurement_theta_min     ?
_cell_measurement_theta_max     ?
_cell_measurement_temperature     123(2)
_exptl_crystal_description     block
_exptl_crystal_colour     colourless
_exptl_crystal_size_max     0.23
_exptl_crystal_size_mid     0.13
_exptl_crystal_size_min     0.09
_exptl_crystal_density_diffrn     1.368
_exptl_crystal_density_meas     ?
_exptl_crystal_density_method     'not measured'
_exptl_crystal_F_000     64
_exptl_absorpt_coefficient_mu     ?
_exptl_absorpt_correction_type     none
_exptl_absorpt_process_details     ?
_exptl_absorpt_correction_T_min     ?
_exptl_absorpt_correction_T_max     ?
_exptl_special_details
;
 ?
;
_diffrn_ambient_temperature     123(2)
_diffrn_radiation_type     'synchrotron'
_diffrn_radiation_wavelength     0.59960(10)
_diffrn_radiation_source     'bending magnet'
_diffrn_radiation_monochromator     'Si(111) double crystal monochromator'
_diffrn_measurement_device_type
;
KM6-CH six-circle κ diffractometer operated as standard four-circle
κ diffractometer with detector circle in the vertical plane to profit
from the linear polarization of the synchrotron beam.
;
_diffrn_measurement_method     ω-scan
_diffrn_detector_area_resol_mean     ?
_diffrn_reflns_number     3942
_diffrn_reflns_av_R_equivalents     0.0141
_diffrn_reflns_theta_min     3.67
_diffrn_reflns_theta_max     59.82
_diffrn_reflns_theta_full     59.82
_diffrn_measured_fraction_theta_max     0.938
_diffrn_measured_fraction_theta_full     0.938
_diffrn_reflns_limit_h_min     -15
_diffrn_reflns_limit_h_max     15
_diffrn_reflns_limit_k_min     -15
_diffrn_reflns_limit_k_max     0
_diffrn_reflns_limit_l_min     -13
_diffrn_reflns_limit_l_max     0
_diffrn_standards_number     ?
_diffrn_standards_interval_count     ?
_diffrn_standards_interval_time     ?
_diffrn_standards_decay_%     ?
_refine_special_details
;
 Charge density refinement. H positional and displacement parameters fixed at
 values from neutron study (Swaminathan et al. (1984) Acta Cryst. B40, 300-306.
;
_reflns_number_total     1045
_reflns_number_gt     817
_reflns_threshold_expression     >2sigma(I)
_refine_ls_structure_factor_coef     Fsqd
_refine_ls_matrix_type     full
_refine_ls_R_factor_all     0.0204
_refine_ls_wR_factor_ref     0.0104
_refine_ls_goodness_of_fit_ref     1.1661
_refine_ls_restrained_S_all     1.1661
_refine_ls_number_reflns     1045
_refine_ls_number_parameters     77
_refine_ls_number_restraints     0
_refine_ls_hydrogen_treatment     refall
_refine_ls_weighting_scheme     calc
_refine_ls_weighting_details     'w=1/[σ^2^(Fo^2]'
_atom_sites_solution_hydrogens     geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary     difmap
_refine_ls_shift/su_max     0.000
_refine_ls_shift/su_mean     0.000
_refine_ls_extinction_method     none
_refine_ls_extinction_coef     '0.0000016(3) rad^2'
_atom_type_scat_source
;
Charge density refinement.
;
_computing_data_collection     'KM6-CH software'
_computing_cell_refinement     'KM6-CH software'
_computing_data_reduction     'XD_RED'
_computing_structure_solution     ?
_computing_structure_refinement     'VALRAY'
_computing_molecular_graphics     ?
_computing_publication_material     ?
loop_
    _atom_site_label
    _atom_site_fract_x
    _atom_site_fract_y
    _atom_site_fract_z
    _atom_site_U_iso_or_equiv
    _atom_site_adp_type
    _atom_site_occupancy
    _atom_site_type_symbol
    C 0.0 0.5 0.32821(3) 0.01238(2) Uani 1 C
    O 0.0 0.5 0.59634(10) 0.01527(2) Uani 1 O
    N 0.14468(7) 0.64468(7) 0.17901(10) 0.02273(3) Uani 1 N
    H1 0.2557(4) 0.7557(4) 0.2841(4) 0.0365(6) Uani 1 H
    H2 0.1431(4) 0.6431(4) -0.0348(3) 0.0333(5) Uani 1 H
loop_
    _atom_site_aniso_label
    _atom_site_aniso_U_11
    _atom_site_aniso_U_22
    _atom_site_aniso_U_33
    _atom_site_aniso_U_12
    _atom_site_aniso_U_13
    _atom_site_aniso_U_23
    O 0.01958(4) 0.01958(4) 0.00665(3) 0.00164(8) 0.000 0.000
    C 0.01519(4) 0.01519(4) 0.00675(4) -0.00035(6) 0.000 0.000
    N 0.02931(6) 0.02931(6) 0.00956(4) -0.01570(7) 0.00002(3) 0.00002(3)
    H1 0.0440(11) 0.0440(11) 0.0216(7) -0.0222(8) -0.0031(9) -0.0031(9)
    H2 0.0430(10) 0.0430(10) 0.0140(6) -0.0158(8) 0.0019(8) 0.0019(8)
_geom_special_details
;
;
loop_
    _geom_bond_atom_site_label_1
    _geom_bond_atom_site_label_2
    _geom_bond_site_symmetry_2
    _geom_bond_distance
    _geom_bond_publ_flag
    O C . 1.2565(5) ?
    C N . 1.3384(4) ?
    N H1 . 1.005(2) ?
    N H2 . 1.0020(15) ?
loop_
    _geom_angle_atom_site_label_1
    _geom_angle_atom_site_label_2
    _geom_angle_atom_site_label_3
    _geom_angle_site_symmetry_1
    _geom_angle_site_symmetry_3
    _geom_angle
    _geom_angle_publ_flag
    O C N . . 121.49(2) ?
    C N H1 . . 119.16(12) ?
    C N H2 . . 120.78(13) ?
    H1 N H2 . . 120.06(17) ?
