data_1008805 _chemical_name_systematic 'Disamarium disilicate' _chemical_formula_structural 'Sm2 (Si2 O7)' _chemical_formula_sum 'O7 Si2 Sm2' _publ_section_title ; Structure investigations of the high-temperature phases of La2 Si2 O7, Gd2 Si2 O7 and Sm2 Si2 O7 ; loop_ _publ_author_name 'Norlund=Christensen, A' 'Frost=Jensen, A' 'Kruse=Themsen, B' 'Gronbaek=Hazell, R' 'Hanfland, M' 'Dooryhee, E' _journal_name_full 'Acta Chemica Scandinavica (43,1989-)' _journal_coden_ASTM ACHSE7 _journal_volume 51 _journal_year 1997 _journal_page_first 1178 _journal_page_last 1185 _cell_length_a 8.553(5) _cell_length_b 12.849(5) _cell_length_c 5.392(2) _cell_angle_alpha 91.08(2) _cell_angle_beta 88.61(4) _cell_angle_gamma 89.68(4) _cell_volume 592.3 _cell_formula_units_Z 4 _symmetry_space_group_name_H-M 'P -1' _symmetry_Int_Tables_number 2 _symmetry_cell_setting triclinic loop_ _symmetry_equiv_pos_as_xyz 'x,y,z' '-x,-y,-z' loop_ _atom_type_symbol _atom_type_oxidation_number Sm3+ 3.000 Si4+ 4.000 O2- -2.000 loop_ _atom_site_label _atom_site_type_symbol _atom_site_symmetry_multiplicity _atom_site_Wyckoff_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_occupancy _atom_site_attached_hydrogens _atom_site_calc_flag Sm1 Sm3+ 2 i 0.1854(1) 0.7678(1) 0.2418(2) 1. 0 d Sm2 Sm3+ 2 i 0.4009(1) 0.5916(1) 0.7565(2) 1. 0 d Sm3 Sm3+ 2 i 0.2987(1) 0.2662(1) 0.7568(2) 1. 0 d Sm4 Sm3+ 2 i 0.1029(1) 0.0886(1) 0.2588(2) 1. 0 d Si1 Si4+ 2 i -0.0029(8) 0.3201(4) 0.2804(11) 1. 0 d Si2 Si4+ 2 i 0.2489(8) 0.9762(5) 0.7135(11) 1. 0 d Si3 Si4+ 2 i 0.2459(8) 0.4794(5) 0.2158(11) 1. 0 d Si4 Si4+ 2 i 0.5038(8) 0.8218(5) 0.7807(11) 1. 0 d O1 O2- 2 i 0.3517(20) 0.4200(13) -0.0025(29) 1. 0 d O2 O2- 2 i 0.1444(20) 0.9203(12) 0.4933(28) 1. 0 d O3 O2- 2 i 0.0812(19) 0.2585(12) 0.5078(26) 1. 0 d O4 O2- 2 i 0.8175(19) 0.3235(13) 0.3733(27) 1. 0 d O5 O2- 2 i 0.0237(21) 0.2478(13) 0.0317(31) 1. 0 d O6 O2- 2 i 0.4135(21) 0.7627(12) 0.0046(32) 1. 0 d O7 O2- 2 i 0.2428(21) 0.0961(12) 0.6399(33) 1. 0 d O8 O2- 2 i 0.6778(20) 0.8345(12) 0.8794(29) 1. 0 d O9 O2- 2 i 0.2428(19) 0.5958(12) 0.1282(30) 1. 0 d O10 O2- 2 i 0.0691(19) 0.4369(14) 0.2350(32) 1. 0 d O11 O2- 2 i 0.3435(22) 0.4621(14) 0.4625(29) 1. 0 d O12 O2- 2 i 0.4992(22) 0.7448(14) 0.5372(33) 1. 0 d O13 O2- 2 i 0.1524(22) 0.9495(14) 0.9693(30) 1. 0 d O14 O2- 2 i 0.4275(18) 0.9354(13) 0.7187(32) 1. 0 d loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_12 _atom_site_aniso_U_13 _atom_site_aniso_U_22 _atom_site_aniso_U_23 _atom_site_aniso_U_33 Sm1 0.0095(6) 0.0005(4) 0.0020(4) 0.0057(5) 0.0001(4) 0.0061(5) Sm2 0.0074(6) 0.0006(4) -0.0002(4) 0.0058(5) 0.0007(4) 0.0045(5) Sm3 0.0089(6) -0.0005(4) -0.0013(4) 0.0070(5) -0.0017(4) 0.0066(5) Sm4 0.0072(6) -0.0007(4) .0000(4) 0.0056(5) 0.0006(4) 0.0048(5) Si1 0.0125(35) -0.0018(22) -0.0026(23) 0.0040(26) 0.0016(21) 0.0048(27) Si2 0.0075(33) 0.0024(21) 0.0007(22) 0.0050(25) 0.0004(21) 0.0047(27) Si3 0.0139(35) 0.0003(22) -0.0017(23) 0.0018(24) -0.0003(21) 0.0052(27) Si4 0.0078(34) -0.0009(23) 0.0011(23) 0.0084(27) 0.0032(22) 0.0056(27) O1 0.0076(90) -0.0047(64) -0.0058(62) 0.0169(82) -0.0021(64) 0.0080(77) O2 0.0133(94) 0.0003(62) 0.0001(63) 0.0093(74) -0.0004(60) 0.0070(75) O3 0.0059(84) 0.0009(58) -0.0105(56) 0.0131(73) -0.0034(56) .0000(65) O4 0.0050(85) 0.0083(62) -0.0051(57) 0.0186(80) 0.0123(60) 0.0039(70) O5 0.0093(92) 0.0001(62) 0.0067(65) 0.0111(77) 0.0035(64) 0.0133(82) O6 0.0130(98) -0.0052(62) 0.0127(71) 0.0053(71) 0.0058(65) 0.0225(91) O7 0.0160(99) -0.0018(60) -0.0114(73) 0.0006(65) -0.0006(64) 0.0237(94) O8 0.0110(92) -0.0026(61) 0.0048(63) 0.0098(74) 0.0058(61) 0.0109(78) O9 0.0026(83) 0.0016(57) 0.0024(61) 0.0093(71) -0.0064(62) 0.0140(82) O10 0.0117(72) 0.0034(58) -0.0003(59) 0.0240(89) 0.0151(71) 0.0268(93) O11 0.0214(109) 0.0016(72) 0.0014(67) 0.0184(88) 0.0017(64) 0.0036(74) O12 0.0151(101) -0.0025(67) 0.0020(7) 0.0124(81) -0.0024(69) 0.0179(91) O13 0.0159(100) -0.0103(72) 0.0027(66) 0.0205(89) -0.0032(66) 0.0062(77) O14 0.0076(77) -0.0049(55) 0.0025(62) 0.0119(75) 0.0120(66) 0.0263(92) _refine_ls_R_factor_all 0.077