data_global _chemical_name_mineral 'Gehlenite' loop_ _publ_author_name 'Swainson I P' 'Dove M T' 'Schmahl W W' 'Putnis A' _journal_name_full 'Physics and Chemistry of Minerals' _journal_volume 19 _journal_year 1992 _journal_page_first 185 _journal_page_last 195 _publ_section_title ; Neutron powder diffraction study of the akermanite-gehlenite solid solution series Sample: O% Ak ; _database_code_amcsd 0007694 _chemical_formula_sum 'Ca2 Al2.06 Si.95 O7' _cell_length_a 7.6850 _cell_length_b 7.6850 _cell_length_c 5.0636 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 299.052 _exptl_crystal_density_diffrn 3.047 _symmetry_space_group_name_H-M 'P -4 21 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 _atom_site_occupancy Ca 0.33890 0.16110 0.51040 1.00000 AlT1 0.00000 0.00000 0.00000 1.00000 AlT2 0.14340 0.35560 0.95400 0.26500 SiT2 0.14340 0.35560 0.95400 0.23750 O1 0.50000 0.00000 0.17650 1.00000 O2 0.14270 0.35730 0.28350 1.00000 O3 0.08760 0.16780 0.80780 1.00000 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 Ca 0.02429 0.02429 0.00747 0.00823 -0.00164 -0.00164 AlT1 0.00859 0.00859 0.00963 0.00000 0.00000 0.00000 AlT2 0.00631 0.00631 0.00253 -0.00099 0.00089 0.00089 SiT2 0.00631 0.00631 0.00253 -0.00099 0.00089 0.00089 O1 0.01544 0.01544 0.00531 -0.00404 0.00000 0.00000 O2 0.01720 0.01720 0.00848 0.00000 0.00329 0.00329 O3 0.01975 0.01101 0.00974 -0.00341 0.00467 -0.00024