data_global _amcsd_formula_title 'Tm2Si2O7' loop_ _publ_author_name 'Fleet M E' 'Liu X' _journal_name_full 'American Mineralogist' _journal_volume 89 _journal_year 2004 _journal_page_first 396 _journal_page_last 404 _publ_section_title ; A new rare earth disilicate (REE2Si2O7: REE = Dy, Tm, Lu; type-L): Evidence for nonquenchable 10 GPa polymorph with silicon in fivefold trigonal bipyramidal coordination? ; _database_code_amcsd 0003423 _chemical_formula_sum 'Tm5.902 Si6 O21' _cell_length_a 6.5499 _cell_length_b 6.5876 _cell_length_c 17.8916 _cell_angle_alpha 83.828 _cell_angle_beta 88.368 _cell_angle_gamma 88.152 _cell_volume 766.872 _exptl_crystal_density_diffrn 6.503 _symmetry_space_group_name_H-M 'P -1' loop_ _space_group_symop_operation_xyz 'x,y,z' '-x,-y,-z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_occupancy _atom_site_U_iso_or_equiv Tm1 0.54372 0.03118 0.25872 0.98000 0.00630 Tm2 0.81604 0.53057 0.26274 0.99100 0.00710 Tm3 0.61586 0.34733 0.09585 0.98500 0.00590 Tm4 0.12118 0.65008 0.09028 0.97100 0.00720 Tm5 0.42926 0.62039 0.41346 0.98400 0.01340 Tm6 0.13580 0.11216 0.39754 0.99100 0.01810 Si1 0.65480 0.13740 0.41900 1.00000 0.00570 Si2 0.63430 0.82310 0.08130 1.00000 0.00550 Si3 0.12310 0.18220 0.06210 1.00000 0.00630 Si4 0.33750 0.51030 0.25870 1.00000 0.00510 Si5 0.00420 0.04230 0.21450 1.00000 0.00490 Si6A 0.95700 0.60170 0.44560 0.50000 0.00600 Si6B 0.90400 0.73320 0.44400 0.50000 0.00500 O1 0.22140 0.07790 0.98900 1.00000 0.01000 O2 0.45540 0.69230 0.05050 1.00000 0.01200 O3 0.91700 0.31080 0.03540 1.00000 0.01000 O4 0.27240 0.34630 0.08650 1.00000 0.00800 O5 0.77810 0.64580 0.12450 1.00000 0.00700 O6 0.56510 0.00930 0.12680 1.00000 0.00900 O7 0.08730 0.98750 0.12700 1.00000 0.00600 O8 0.86980 0.25190 0.19230 1.00000 0.00900 O9 0.14190 0.58800 0.21080 1.00000 0.00900 O10 0.50440 0.37210 0.21490 1.00000 0.00600 O11 0.84860 0.87110 0.24950 1.00000 0.00500 O12 0.19630 0.06050 0.26580 1.00000 0.00700 O13 0.48510 0.69490 0.28020 1.00000 0.01300 O14 0.78930 0.22540 0.34420 1.00000 0.01700 O15 0.27450 0.39890 0.34120 1.00000 0.00900 O16 0.77210 0.61620 0.38570 1.00000 0.01900 O17 0.47630 0.99920 0.38670 1.00000 0.00500 O18 0.12510 0.77570 0.40950 1.00000 0.01300 O19 0.81660 0.98950 0.46740 1.00000 0.02400 O20 0.55240 0.30750 0.46780 1.00000 0.00700 O21 0.11390 0.37250 0.47090 1.00000 0.02500