Investigation of Methacrylic Acid at High Pressure Using Neutron Diffraction.
Marshall, William G.; Urquhart, Andrew J.; Oswald, Iain D. H.; The journal of physical chemistry. B 119 (2015) 12147–12154; doi:10.1021/acs.jpcb.5b07106

data_1554038
_publ_section_title
;
 Investigation of Methacrylic Acid at High Pressure Using Neutron
 Diffraction.
;
_journal_issue                   36
_journal_name_full               'The journal of physical chemistry. B'
_journal_page_first              12147
_journal_page_last               12154
_journal_paper_doi               10.1021/acs.jpcb.5b07106
_journal_volume                  119
_journal_year                    2015
_chemical_formula_moiety         'C4 H6 O2'
_chemical_formula_sum            'C4 H6 O2'
_chemical_formula_weight         86.09
_space_group_IT_number           14
_space_group_name_Hall           '-P 2yn'
_space_group_name_H-M_alt        'P 1 21/n 1'
_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   difmap
_atom_sites_solution_primary     direct
_cell_angle_alpha                90
_cell_angle_beta                 90.36(3)
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   3.6140(7)
_cell_length_b                   16.420(3)
_cell_length_c                   6.773(3)
_cell_measurement_reflns_used    443
_cell_measurement_temperature    293
_cell_measurement_theta_max      19
_cell_measurement_theta_min      2
_cell_volume                     401.9(2)
_computing_cell_refinement       'Apex2 (Bruker AXS, 2006)'
_computing_data_collection       'Apex2 (Bruker AXS, 2006)'
_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         1700000
_diffrn_ambient_temperature      293
_diffrn_measured_fraction_theta_full 0.415
_diffrn_measured_fraction_theta_max 0.377
_diffrn_measurement_device       Area
_diffrn_measurement_device_type  'Bruker Kappa Apex2'
_diffrn_measurement_method       \w
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_type           'Mo K\a'
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.053
_diffrn_reflns_limit_h_max       4
_diffrn_reflns_limit_h_min       -4
_diffrn_reflns_limit_k_max       17
_diffrn_reflns_limit_k_min       -13
_diffrn_reflns_limit_l_max       3
_diffrn_reflns_limit_l_min       -3
_diffrn_reflns_number            900
_diffrn_reflns_theta_full        17.399
_diffrn_reflns_theta_max         23.199
_diffrn_reflns_theta_min         4.966
_diffrn_standards_number         0
_exptl_absorpt_coefficient_mu    0.114
_exptl_absorpt_correction_T_max  0.99
_exptl_absorpt_correction_T_min  0.78
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'SADABS (Siemens, 1996)'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.423
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       plate
_exptl_crystal_F_000             184
_exptl_crystal_size_max          0.100
_exptl_crystal_size_mid          0.050
_exptl_crystal_size_min          0.050
_refine_diff_density_max         0.16
_refine_diff_density_min         -0.15
_refine_ls_extinction_method     None
_refine_ls_goodness_of_fit_ref   1.1640
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     56
_refine_ls_number_reflns         124
_refine_ls_number_restraints     52
_refine_ls_R_factor_all          0.1112
_refine_ls_R_factor_gt           0.0551
_refine_ls_shift/su_max          0.0000766
_refine_ls_shift/su_mean         0.0000245
_refine_ls_structure_factor_coef F
_refine_ls_weighting_details
;
 Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) 
 [weight] = 1.0/[A~0~*T~0~(x)+A~1~*T~1~(x) ... +A~n-1~]*T~n-1~(x)] 
 where A~i~ are the Chebychev coefficients listed below and x= Fcalc/Fmax 
 Method = Robust Weighting (Prince, 1982) 
 W = [weight] * [1-(deltaF/6*sigmaF)^2^]^2^ 
 A~i~ are: 
 0.725 0.473 0.507 
;
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_all         0.1434
_refine_ls_wR_factor_gt          0.0474
_refine_ls_wR_factor_ref         0.0474
_reflns_limit_h_max              4
_reflns_limit_h_min              -3
_reflns_limit_k_max              17
_reflns_limit_k_min              0
_reflns_limit_l_max              3
_reflns_limit_l_min              0
_reflns_number_gt                123
_reflns_number_total             214
_reflns_threshold_expression     I>2.0\s(I)
_oxford_diffrn_Wilson_B_factor   2.45
_oxford_diffrn_Wilson_scale      3.56
_oxford_refine_ls_r_factor_ref   0.0551
_oxford_refine_ls_scale          0.565(7)
_oxford_reflns_number_all        213
_oxford_reflns_threshold_expression_ref I>2.0\s(I)
_cod_data_source_file            1_SXD.cif
_cod_data_source_block           1_SXD
_cod_original_cell_volume        401.91(17)
_cod_original_sg_symbol_H-M      'P 1 21/n 1 '
_cod_database_code               1554038