data_1100916
_journal_name_full     'Acta Crystallographica, Section C'
_journal_year     2000
_journal_volume     56
_journal_page_first     916
_journal_page_last     918
_publ_section_title
;
Structural study of AgNbO~3~ at room temperature
;
loop_
_publ_author_name
    "Fabry, Jan"
    'Zikmund, Zdenek'
    'Kania, Antoni'
    "Petricek, Vaclav"
_publ_section_synopsis
;
AgNbO~3~ is a tilted perovskite which is isostructural with NaNbO~3~ at room
temperature.
;
_chemical_name_systematic
;
silver niobate
;
_chemical_formula_moiety     'Ag Nb O3'
_chemical_formula_sum     'Ag Nb O3'
_chemical_formula_structural     'Ag Nb O3'
_chemical_formula_iupac     'Ag Nb O3'
_chemical_formula_weight     248.77
_symmetry_cell_setting     orthorhombic
_symmetry_space_group_name_H-M     'P b c m'
loop_
    _symmetry_equiv_pos_as_xyz
    'x, y, z'
    'x, y, -z+1/2'
    '-x, y+1/2, z'
    '-x, y+1/2, -z+1/2'
    '-x, -y, -z'
    '-x, -y, z+1/2'
    'x, -y+1/2, -z'
    'x, -y+1/2, z+1/2'
_cell_length_a     5.5462(3)
_cell_length_b     5.6028(4)
_cell_length_c     15.6365(13)
_cell_angle_alpha     90.00
_cell_angle_beta     90.00
_cell_angle_gamma     90.00
_cell_volume     485.90(6)
_cell_formula_units_Z     8
_cell_measurement_reflns_used     50
_cell_measurement_theta_min     5
_cell_measurement_theta_max     33
_cell_measurement_temperature     292.0(10)
_exptl_crystal_description     'prism'
_exptl_crystal_colour     'light brown'
_exptl_crystal_size_max      .31
_exptl_crystal_size_mid      .17
_exptl_crystal_size_min      .09
_exptl_crystal_density_diffrn     6.799
_exptl_crystal_density_meas     'not measured'
_exptl_crystal_density_method     ?
_exptl_crystal_F_000     896
_exptl_absorpt_coefficient_mu     12.492
_exptl_absorpt_correction_type     'Gaussian'
_exptl_absorpt_process_details     '(Templeton & Templeton, 1978)'
_exptl_absorpt_correction_T_min      .130
_exptl_absorpt_correction_T_max      .356
_diffrn_radiation_type     'Mo K\a'
_diffrn_radiation_wavelength      .71073
_diffrn_measurement_device     'Hilger & Watts'
_diffrn_measurement_method     \w/2\q
_diffrn_reflns_number     5156
_diffrn_reflns_av_R_equivalents      .025
_diffrn_reflns_theta_max     30
_diffrn_reflns_theta_full     30
_diffrn_reflns_limit_h_min     -7
_diffrn_reflns_limit_h_max     7
_diffrn_reflns_limit_k_min     -7
_diffrn_reflns_limit_k_max     7
_diffrn_reflns_limit_l_min     -21
_diffrn_reflns_limit_l_max     22
_diffrn_standards_number     3
_diffrn_standards_interval_count     30
_diffrn_standards_interval_time     ?
_diffrn_standards_decay_%     7.0
_reflns_number_total     1689
_reflns_number_gt     1497
_reflns_threshold_expression     I>3\s(I)
_refine_ls_structure_factor_coef     F
_refine_ls_matrix_type     fullcycle
_refine_ls_R_factor_gt      .034
_refine_ls_wR_factor_ref      .053
_refine_ls_goodness_of_fit_all     2.69
_refine_ls_goodness_of_fit_ref     2.84
_refine_ls_number_reflns     1689
_refine_ls_number_parameters     52
_refine_ls_number_constraints     0
_refine_ls_hydrogen_treatment     none
_refine_ls_weighting_scheme     'w = (\s^2^(F~o~)+0.0001(F~o~)^2^)^-1^'
_refine_ls_shift/su_max      .01
_refine_diff_density_max     1.20
_refine_diff_density_min     -3.65
_refine_ls_extinction_method     'type II (Becker & Coppens, 1974)'
_refine_ls_extinction_coef      .000228(4)
loop_
    _atom_type_symbol
    _atom_type_scat_dispersion_real
    _atom_type_scat_dispersion_imag
    _atom_type_scat_source
    Ag  -.897 1.102 International_Tables_vol_IV_Table_2.2A_and_2.3.1
    Nb -2.073  .622 International_Tables_vol_IV_Table_2.2A_and_2.3.1
    O  .011  .006 International_Tables_vol_IV_Table_2.2A_and_2.3.1
loop_
    _atom_site_U_iso_or_equiv
    _atom_site_label
    _atom_site_fract_z
    _atom_site_fract_x
    _atom_site_fract_y
    _atom_site_adp_type
    _atom_site_occupancy
    _atom_site_type_symbol
     .01280(10) Ag1  3/4  .75770(3) 0.22738(7)
                                            Uani 1 Ag
     .01280(10) Ag2 1/2 .75550(3) 1/4
                                     Uani 1 Ag
    .00590(10) Nb    0.625014(8)  .74525(2) 0.72338(7)
                                                   Uani 1 Nb
      .0090(4) O1  3/4 .6978(2) 0.7664(2) Uani 1 O
    .0095(4) O2  1/2 .8043(2) 3/4  Uani 1 O
     .0088(3) O3   0.61132(6) .4662(2) 0.5364(2) Uani 1 O
    .0092(3) O4    0.63865(7) -.0334(2) 0.4727(2)   Uani 1 O
loop_
    _atom_site_aniso_label
    _atom_site_aniso_U_22
    _atom_site_aniso_U_11
    _atom_site_aniso_U_33
    _atom_site_aniso_U_12
    _atom_site_aniso_U_13
    _atom_site_aniso_U_23
    _atom_site_aniso_type_symbol
    Ag1   .0123(2) .0128(2)   .0133(2)  -.00211(4)  .0000  .0000 Ag
    Ag2  .01410(10) .0113(2)
                             .0130(2)  .0000
                                 .0000  .00107(7) Ag
    Nb  .0040(2)  .0051(2)   .0085(2)  -.00014(3)  -.00061(4)  .00031(4) Nb
    O1  .0119(7) .0118(6)   .0031(7)  .0009(4)  .0000  .0000 O
    O2  .0127(6) .0100(6)   .0059(7)  .0000  .0000  .0004(4) O
    O3  .0084(5) .0064(4)    .0115(5)  -.0033(3)  -.0013(3)  .0014(3) O
    O4  .0077(5) .0086(4)   .0114(5)  .0030(3)
                                               .0010(3)
                                                             .0013(3) O