data_Modulated structure of Sr2Nb2O7 _cell_length_a 3.9537(6) _cell_length_b 26.749(4) _cell_length_c 5.7002(10) _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 614.71(17) _cell_measurement_pressure ? _cell_measurement_radiation ? _cell_measurement_reflns_used ? _cell_measurement_temperature ? _cell_measurement_theta_max ? _cell_measurement_theta_min ? _cell_measurement_wavelength ? _cell_modulation_dimension 1 loop_ _cell_wave_vector_seq_id _cell_wave_vector_x _cell_wave_vector_y _cell_wave_vector_z 1 0.48800 0.00000 0.00000 _cell_formula_units_Z 4 _symmetry_cell_setting orthorhombic _symmetry_ssg_name_IT Cmc21(\a00)0s loop_ _symmetry_ssg_equiv_pos_seq_id _symmetry_ssg_equiv_pos_as_xyz 1 x1,x2,x3,x4 2 x1,-x2,1/2+x3,1/2+x4 3 -x1,-x2,1/2+x3,-x4 4 -x1,x2,x3,1/2-x4 5 1/2+x1,1/2+x2,x3,x4 6 1/2+x1,1/2-x2,1/2+x3,1/2+x4 7 1/2-x1,1/2-x2,1/2+x3,-x4 8 1/2-x1,1/2+x2,x3,1/2-x4 loop_ _atom_type_symbol _atom_type_oxidation_number _atom_type_number_in_cell _atom_type_scat_dispersion_real _atom_type_scat_dispersion_imag _atom_type_scat_source _atom_type_scat_Cromer_Mann_a1 _atom_type_scat_Cromer_Mann_b1 _atom_type_scat_Cromer_Mann_a2 _atom_type_scat_Cromer_Mann_b2 _atom_type_scat_Cromer_Mann_a3 _atom_type_scat_Cromer_Mann_b3 _atom_type_scat_Cromer_Mann_a4 _atom_type_scat_Cromer_Mann_b4 _atom_type_scat_Cromer_Mann_c Sr 0 16 -0.117 2.203 International_Tables_Vol_C 17.566299 1.5564 9.8184 14.0988 5.422 0.1664 2.6694 132.376007 2.5064 Nb 0 16 -0.828 2.840 International_Tables_Vol_C 17.614201 1.18865 12.0144 11.766 4.04183 0.204785 3.53346 69.7957 3.75591 O 0 56 0.006 0.004 International_Tables_Vol_C 3.0485 13.2771 2.2868 5.7011 1.5463 0.3239 0.867 32.908901 0.2508 _chemical_formula_sum 'Sr2 Nb2 O7' _chemical_formula_weight 473 _exptl_crystal_colour ? _exptl_crystal_description ? _exptl_crystal_size_max ? _exptl_crystal_size_mid ? _exptl_crystal_size_min ? _exptl_crystal_size_rad ? _exptl_crystal_density_diffrn 5.11 _exptl_crystal_density_meas ? _exptl_crystal_density_meas_temp ? _exptl_crystal_density_method ? _exptl_crystal_F_000 856 _exptl_absorpt_correction_type none _exptl_absorpt_coefficient_mu ? _exptl_absorpt_correction_T_min 1.000 _exptl_absorpt_correction_T_max 1.000 _diffrn_measurement_device 'imaging plate system' _diffrn_measurement_device_type 'IPDS Stoe' _diffrn_measurement_method '??integration method??' _diffrn_radiation_probe 'X-ray' _diffrn_radiation_type ? _diffrn_radiation_wavelength 0.5 _diffrn_standards_number ? _diffrn_standards_decay_% ? _diffrn_standards_interval_count ? _diffrn_standards_interval_time ? _diffrn_reflns_limit_h_min -9 _diffrn_reflns_limit_h_max 8 _diffrn_reflns_limit_k_min -64 _diffrn_reflns_limit_k_max 62 _diffrn_reflns_limit_l_min -13 _diffrn_reflns_limit_l_max 8 _diffrn_reflns_limit_index_m_1_min -1 _diffrn_reflns_limit_index_m_1_max 1 _reflns_limit_h_min 0 _reflns_limit_h_max 9 _reflns_limit_k_min 0 _reflns_limit_k_max 64 _reflns_limit_l_min -13 _reflns_limit_l_max 8 _reflns_limit_index_m_1_min -1 _reflns_limit_index_m_1_max 1 _diffrn_reflns_number 18977 _diffrn_reflns_theta_min 1.07 _diffrn_reflns_theta_max 37.61 _diffrn_reflns_av_R_equivalents 0.0742 _diffrn_reflns_av_sigmaI/netI 0.0075 _reflns_observed_criterion 3 _reflns_number_total 5126 _reflns_number_observed 4888 _refine_ls_structure_factor_coef F _refine_ls_weighting_scheme sigma _refine_ls_weighting_details 'w=1/(\s^2^(F)+0.0004F^2^)' _refine_ls_R_factor_gt 0.0565 _refine_ls_wR_factor_gt 0.0824 _refine_ls_R_factor_all 0.0594 _refine_ls_wR_factor_ref 0.0842 _refine_ls_number_reflns 5126 _refine_ls_number_parameters 105 _refine_ls_goodness_of_fit_ref 3.26 _refine_ls_goodness_of_fit_obs 3.26 _refine_ls_shift/su_max 0.0005 _refine_ls_shift/su_mean 0.0000 _refine_diff_density_max ? _refine_diff_density_min ? _refine_ls_extinction_method 'none' _refine_ls_extinction_coef ? loop_ _atom_site_label _atom_site_type_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_symmetry_multiplicity _atom_site_occupancy Sr1 Sr 0.5 0.20587(2) 0.02976(16) 0.01184(12) 4 1 Sr2 Sr 0.5 0.051848(15) 0.46660(13) 0.00606(7) 4 1 Nb1 Nb 0 0.162003(12) 0.5 0.00324(5) 4 1 Nb2 Nb 0.5 0.442230(11) 0.47044(9) 0.00229(5) 4 1 O1 O 0 0.00700(14) 0.2221(8) 0.0083(8) 4 1 O2 O 0 0.10988(18) 0.1772(11) 0.0144(12) 4 1 O3 O 0.5 0.15090(15) 0.4728(10) 0.0107(10) 4 1 O4 O 0 0.21408(16) 0.2857(9) 0.0080(7) 4 1 O5 O 0.5 0.30052(19) 0.2640(10) 0.0105(9) 4 1 O6 O 0.5 0.40684(14) 0.1710(8) 0.0078(6) 4 1 O7 O 0 0.45098(16) 0.4511(11) 0.0092(8) 4 1 loop_ _atom_site_aniso_label _atom_site_aniso_type_symbol _atom_site_adp_type _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 Sr1 Sr Uani 0.00386(11) 0.0221(2) 0.0090(2) 0 0 0.0054(2) Sr2 Sr Uani 0.00394(10) 0.00764(11) 0.00637(15) 0 0 -0.00139(12) Nb1 Nb Uani 0.00206(8) 0.00394(8) 0.00359(11) 0 0 0.00035(7) Nb2 Nb Uani 0.00125(8) 0.00352(7) 0.00199(10) 0 0 -0.00014(7) O1 O Uani 0.0113(17) 0.0059(10) 0.0073(14) 0 0 0.0024(9) O2 O Uani 0.025(3) 0.0083(12) 0.0096(16) 0 0 -0.0026(13) O3 O Uani 0.0021(7) 0.0097(10) 0.020(2) 0 0 -0.0011(16) O4 O Uani 0.0082(12) 0.0079(11) 0.0074(12) 0 0 0.0038(10) O5 O Uani 0.0111(17) 0.0103(12) 0.0097(15) 0 0 0.0036(11) O6 O Uani 0.0098(13) 0.0073(9) 0.0059(11) 0 0 -0.0019(9) O7 O Uani 0.0022(8) 0.0116(11) 0.014(2) 0 0 0.0009(14) loop_ _atom_site_Fourier_wave_vector_seq_id _atom_site_Fourier_wave_vector_x _atom_site_Fourier_wave_vector_y _atom_site_Fourier_wave_vector_z 1 0.48800 0.00000 0.00000 loop_ _atom_site_displace_Fourier_atom_site_label _atom_site_displace_Fourier_axis _atom_site_displace_Fourier_wave_vector_seq_id _atom_site_displace_Fourier_cos _atom_site_displace_Fourier_sin Sr1 x 1 0.0029(2) 0 Sr1 y 1 0 0.00473(3) Sr1 z 1 0 0.01599(12) Sr2 x 1 0.00021(18) 0 Sr2 y 1 0 -0.00181(2) Sr2 z 1 0 -0.00090(12) Nb1 x 1 0.00298(16) 0 Nb1 y 1 0 0.00050(2) Nb1 z 1 0 0.00067(11) Nb2 x 1 0.00398(16) 0 Nb2 y 1 0 0.00037(2) Nb2 z 1 0 0.00047(11) O1 x 1 -0.0289(17) 0 O1 y 1 0 0.0004(2) O1 z 1 0 0.0003(9) O2 x 1 -0.0471(19) 0 O2 y 1 0 0.0005(2) O2 z 1 0 0.0003(11) O3 x 1 -0.0001(14) 0 O3 y 1 0 -0.0006(2) O3 z 1 0 -0.0318(13) O4 x 1 -0.0170(15) 0 O4 y 1 0 0.0018(2) O4 z 1 0 0.0024(12) O5 x 1 -0.0248(16) 0 O5 y 1 0 -0.0014(2) O5 z 1 0 -0.0031(12) O6 x 1 -0.0166(15) 0 O6 y 1 0 0.0000(2) O6 z 1 0 0.0015(9) O7 x 1 0.0036(15) 0 O7 y 1 0 0.0016(2) O7 z 1 0 -0.0293(12) loop_ _atom_site_U_Fourier_atom_site_label _atom_site_U_Fourier_tens_elem _atom_site_U_Fourier_wave_vector_seq_id _atom_site_U_Fourier_cos _atom_site_U_Fourier_sin Sr1 U11 1 0 0.0005(3) Sr1 U22 1 0 -0.0150(3) Sr1 U33 1 0 -0.0050(4) Sr1 U12 1 0.0006(2) 0 Sr1 U13 1 -0.0001(2) 0 Sr1 U23 1 0 -0.0066(3)