data_global _amcsd_formula_title 'K2 Nb2 O14 Si4' loop_ _publ_author_name 'Crosnier M' 'Guyomard D' 'Verbaere A' 'Piffard Y' 'Tournoux M' _journal_name_full 'Journal of Solid State Chemistry' _journal_volume 98 _journal_year 1992 _journal_page_first 128 _journal_page_last 132 _publ_section_title ; The potassium niobyl cyclotetrasilicate K2(NbO)2Si4O12 _cod_database_code 1000339 ; _database_code_amcsd 0013735 _chemical_formula_sum 'Nb K Si2 O7' _cell_length_a 8.7404 _cell_length_b 8.7404 _cell_length_c 8.136 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 621.546 _exptl_crystal_density_diffrn 3.208 _symmetry_space_group_name_H-M 'P 4 b m' loop_ _space_group_symop_operation_xyz 'x,y,z' '1/2-y,1/2-x,z' '-y,x,z' '1/2+x,1/2-y,z' '-x,-y,z' '1/2+y,1/2+x,z' 'y,-x,z' '1/2-x,1/2+y,z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z Nb1 0.00000 0.00000 0.21600 Nb2 0.00000 0.00000 0.71940 K1 0.32260 0.82260 0.99190 Si1 0.12420 0.62420 0.30150 Si2 0.12400 0.62400 0.69380 O1 0.42510 0.28820 0.23300 O2 0.42190 0.28920 0.76540 O3 0.00000 0.00000 0.00000 O4 0.00000 0.00000 0.50100 O5 0.12000 0.62000 0.49680 O6 0.50000 0.00000 0.22800 O7 0.50000 0.00000 0.76280 loop_ _atom_site_aniso_label _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 Nb1 0.00710 0.00710 0.00790 0.00000 0.00000 0.00000 Nb2 0.00640 0.00640 0.00790 0.00000 0.00000 0.00000 K1 0.01800 0.01800 0.01240 -0.00340 0.00050 0.00050 Si1 0.00760 0.00760 0.00390 0.00070 0.00040 0.00040 Si2 0.00710 0.00710 0.00360 -0.00010 -0.00030 -0.00030