A new polymorph of N,N'-dimethylurea characterized by X-ray diffraction and first-principles lattice dynamics calculations.
Martins, David M. S.; Spanswick, Christopher K.; Middlemiss, Derek S.; Abbas, Nasir; Pulham, Colin R.; Morrison, Carole A.; The journal of physical chemistry. A 113 (2009) 5998–6003; doi:10.1021/jp900141q

data_1516355
_publ_section_title
;
 A new polymorph of N,N'-dimethylurea characterized by X-ray diffraction
 and first-principles lattice dynamics calculations.
;
_journal_issue                   20
_journal_name_full               'The journal of physical chemistry. A'
_journal_page_first              5998
_journal_page_last               6003
_journal_paper_doi               10.1021/jp900141q
_journal_volume                  113
_journal_year                    2009
_chemical_absolute_configuration unk
_chemical_compound_source        Sigma-Aldrich
_chemical_formula_moiety         'C3 H8 N2 O1'
_chemical_formula_sum            'C3 H8 N2 O'
_chemical_formula_weight         88.11
_chemical_name_common            1,3-dimethylurea
_chemical_name_systematic        1,3-dimethylurea
_space_group_IT_number           18
_symmetry_cell_setting           orthorhombic
_symmetry_Int_Tables_number      18
_symmetry_space_group_name_Hall  'P 2 2ab'
_symmetry_space_group_name_H-M   'P 21 21 2'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            2
_cell_length_a                   4.9790(10)
_cell_length_b                   10.775(2)
_cell_length_c                   4.5764(9)
_cell_measurement_reflns_used    1629
_cell_measurement_temperature    150
_cell_measurement_theta_max      29
_cell_measurement_theta_min      4
_cell_volume                     245.52(8)
_computing_cell_refinement       'SAINT (Siemens ,1995)'
_computing_data_collection       'SMART (Siemens, 1993)'
_computing_data_reduction        'SAINT (Siemens ,1995)'
_computing_molecular_graphics    'CAMERON (Watkin et al., 1996)'
_computing_publication_material  'CRYSTALS (Betteridge et al., 2003)'
_computing_structure_refinement  'CRYSTALS (Betteridge et al., 2003)'
_computing_structure_solution    'SIR92 (Altomare et al., 1994)'
_diffrn_ambient_pressure         amb
_diffrn_ambient_temperature      150
_diffrn_measured_fraction_theta_full 1.000
_diffrn_measured_fraction_theta_max 0.983
_diffrn_measurement_device       'Bruker SMART'
_diffrn_measurement_device_type  Area
_diffrn_measurement_method       \w
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_probe          x-ray
_diffrn_radiation_type           'Mo K\a'
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.030
_diffrn_reflns_limit_h_max       6
_diffrn_reflns_limit_h_min       -6
_diffrn_reflns_limit_k_max       14
_diffrn_reflns_limit_k_min       -14
_diffrn_reflns_limit_l_max       5
_diffrn_reflns_limit_l_min       -6
_diffrn_reflns_number            2933
_diffrn_reflns_theta_full        27.595
_diffrn_reflns_theta_max         28.745
_diffrn_reflns_theta_min         3.782
_diffrn_standards_number         0
_exptl_absorpt_coefficient_mu    0.091
_exptl_absorpt_correction_T_max  0.98
_exptl_absorpt_correction_T_min  0.82
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'SADABS (Siemens, 1996)'
_exptl_crystal_colour            colorless
_exptl_crystal_density_diffrn    1.192
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       block
_exptl_crystal_F_000             96
_exptl_crystal_recrystallization_method pure
_exptl_crystal_size_max          0.31
_exptl_crystal_size_mid          0.28
_exptl_crystal_size_min          0.22
_refine_diff_density_max         0.15
_refine_diff_density_min         -0.16
_refine_ls_extinction_method     None
_refine_ls_goodness_of_fit_ref   1.0036
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     29
_refine_ls_number_reflns         395
_refine_ls_number_restraints     0
_refine_ls_R_factor_all          0.0470
_refine_ls_R_factor_gt           0.0362
_refine_ls_shift/su_max          0.000176
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
;
 Method= Modified Sheldrick 
 w=1/[\s^2^(F^2^) + ( 0.03P)^2^ + 0.04P] 
 ,where P=(max(Fo^2^,0) + 2Fc^2^)/3 
;
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_all         0.0919
_refine_ls_wR_factor_gt          0.0892
_refine_ls_wR_factor_ref         0.0919
_reflns_limit_h_max              6
_reflns_limit_h_min              0
_reflns_limit_k_max              14
_reflns_limit_k_min              0
_reflns_limit_l_max              6
_reflns_limit_l_min              0
_reflns_number_gt                321
_reflns_number_total             395
_reflns_threshold_expression     I>2.0\s(I)
_oxford_diffrn_Wilson_B_factor   2.80
_oxford_diffrn_Wilson_scale      1.10
_oxford_refine_ls_r_factor_ref   0.0470
_oxford_refine_ls_scale          0.966(8)
_oxford_reflns_number_all        395
_oxford_reflns_threshold_expression_ref I>-10.0\s(I)
_cod_data_source_file            jp900141q_si_001.cif
_cod_data_source_block           1
_cod_original_formula_sum        'C3 H8 N2 O1'
_cod_database_code               1516355