Crystal structures of spinel-type Na~2~MoO~4~ and Na~2~WO~4~ revisited using neutron powder diffraction
Fortes, A. Dominic; Acta Crystallographica Section E 71 (2015) 592–596; doi:10.1107/S2056989015008774

data_2240655
_publ_section_title
;
 Crystal structures of spinel-type Na~2~MoO~4~ and Na~2~WO~4~ revisited
 using neutron powder diffraction
;
_journal_coeditor_code           WM5152
_journal_issue                   6
_journal_name_full               'Acta Crystallographica Section E'
_journal_page_first              592
_journal_page_last               596
_journal_paper_doi               10.1107/S2056989015008774
_journal_volume                  71
_journal_year                    2015
_chemical_formula_iupac          'Na2 Mo O4'
_chemical_formula_structural     'Na2 Mo O4'
_chemical_formula_sum            'Mo Na2 O4'
_chemical_formula_weight         205.92
_chemical_melting_point          961
_chemical_name_common            'sodium molybdate'
_chemical_name_systematic
;
Disodium molybdenum(VI) oxide
;
_space_group_IT_number           227
_symmetry_cell_setting           cubic
_symmetry_space_group_name_Hall  '-F 4vw 2vw 3'
_symmetry_space_group_name_H-M   'F d -3 m :2'
_audit_creation_method           'from EXP file using GSAS2CIF'
_cell_angle_alpha                90.0
_cell_angle_beta                 90.0
_cell_angle_gamma                90.0
_cell_formula_units_Z            8
_cell_length_a                   9.10888(3)
_cell_length_b                   9.108879
_cell_length_c                   9.108879
_cell_measurement_temperature    298
_cell_volume                     755.779(2)
_computing_cell_refinement
;
<i>GSAS/Expgui</i> (Larsen & Von Dreele, 2000; Toby, 2001)
;
_computing_data_collection       '<i>HRPD control software</i>'
_computing_data_reduction
;
<i>MANTID</i> (Arnold <i>et al</i>., 2014; Mantid, 2013)
;
_computing_molecular_graphics
;
DIAMOND (Putz & Brandenburg, 2006)
;
_computing_publication_material
;
publCIF (Westrip, 2010)
;
_computing_structure_refinement
;
<i>GSAS/Expgui</i> (Larsen & Von Dreele, 2000, Toby, 2001)
;
_computing_structure_solution    'coordinates taken from a previous refinement'
_diffrn_ambient_temperature      298
_diffrn_measurement_device_type  'HRPD, High resolution neutron powder'
_diffrn_radiation_type           neutron
_exptl_absorpt_coefficient_mu    '0.014 + 0.0018 * \l'
_exptl_absorpt_correction_T_max  0.99984
_exptl_absorpt_correction_T_min  0.99980
_exptl_absorpt_correction_type   analytical
_exptl_absorpt_process_details
;
Data were corrected for self shielding using \s~scatt~ = 29.198 barns and
 \s~ab~(\l) = 3.541 barns at 1.798 \%A during the normalization procedure. The
 linear absorption coefficient is wavelength dependent and is calculated as: \m
 = 0.014 + 0.0018 * \l  (mm^-1^).
;
_exptl_crystal_density_diffrn    3.6192
_exptl_crystal_density_method    'not measured'
_pd_block_id                     2015-04-07T09:39|NA2MOO4|Fortes|HRPD
_pd_calc_method                  'Rietveld Refinement'
_pd_char_colour                  white
_pd_instr_dist_spec/detc         965
_pd_instr_dist_src/spec          95000
_pd_instr_location
;
High Resolution Powder Diffractometer, ISIS neutron spallation source,
 Rutherford Appleton Laboratory, Oxfordshire, U.K.
;
_pd_meas_2theta_fixed            168.329
_pd_meas_number_of_points        7716
_pd_meas_scan_method             tof
_pd_phase_name                   Na2MoO4
_pd_prep_pressure                100
_pd_prep_temperature             673
_pd_proc_info_data_reduction
;
Both the mass and the volume of the specimen were measured in order to compute
 the packing number density (0.0048 \%A^-3^). The stoichiometry of the compound
 was used
 to calculate the scattering and absorption cross sections (29.198 barns and
 3.541
 barns at \l = 1.798 \%A, respectively) from data tabulated by
 NIST (http://www.ncnr.nist.gov/resources/n-lengths/).
 Together, these data were used by the Mantid normalisation routine to apply
 the appropriate self-shielding correction to the data.
This Mantid routine focuses the data to a common scattering angle and
 normalises the data with respect to the incident neutron spectrum by reference
 to a V:Nb null-scattering rod.
;
_pd_proc_info_excluded_regions
;
Data at d-spacings smaller than 0.4 \%A were excluded since the counting
 statistics became progressively poorer at very short flight times due to the
 lower neutron flux at the shortest wavelengths.
;
_pd_proc_ls_background_function
;   GSAS Background function #1 (10 terms).
 Shifted Chebyshev function of 1st kind
1: 1.18715, 2: -7.466630x10^-3^, 3:8.117230x10^-2^, 4: -5.411800x10^-2^, 5:
 -1.714140x10^-2^, 6: -1.882400x10^-2^, 7: -1.930110x10^-2^, 8:
 -6.255180x10^-3^, 9: 6.598230x10^-3^, 10: 8.478560x10^-3^
;
_pd_proc_ls_peak_cutoff          0.00050
_pd_proc_ls_profile_function
;
TOF profile function #3 (21 terms).
Profile coefficients for exp pseudovoigt
 convolution [Von Dreele, 1990 (unpublished)]
(\a) = 0.1919, (\b~0~) = 0.025953, (\b~1~) = 0.005213,
(\s~0~) = 0, (\s~1~) = 196.3, (\s~2~) = 23.5,
(\g~0~) = 0, (\g~1~) = 14.91, (\g~2~) = 0,
(\g~2s~) = 0, (\g~1e~) = 0, (\g~2e~) = 0,
(\e~i~) = 0, (\e~a~) = 0, (\e~A~) = 0,
(\g~11~) = 0, (\g~22~) = 0, (\g~33~) = 0,
(\g~12~) = 0, (\g~13~) = 0, (\g~23~) = 0.
Peak tails ignored where intensity <0.0005x peak.
  Aniso. broadening axis   0.0   0.0   1.0
;
_pd_proc_ls_prof_R_factor        0.0368
_pd_proc_ls_prof_wR_expected     0.0221
_pd_proc_ls_prof_wR_factor       0.0434
_pd_proc_number_of_points        7716
_pd_spec_mounting                'vanadium tube'
_pd_spec_mount_mode              transmission
_pd_spec_shape                   cylinder
_pd_spec_size_axial              25
_pd_spec_size_equat              11
_refine_ls_goodness_of_fit_all   1.96
_refine_ls_matrix_type           full
_refine_ls_number_constraints    0
_refine_ls_number_parameters     24
_refine_ls_number_restraints     0
_refine_ls_shift/su_max          0.03
_refine_ls_shift/su_mean         0.00
_reflns_number_total             330
_cod_data_source_file            wm5152sup1.cif
_cod_data_source_block           Na~2~MoO~4~
_cod_original_cell_volume        755.779(9)
_cod_original_sg_symbol_H-M      'F d -3 m'
_cod_database_code               2240655