data_global _chemical_name_mineral 'Akermanite' loop_ _publ_author_name 'Mokeeva V' 'Makarov E' _journal_name_full 'Geokhimiya' _journal_volume 10 _journal_year 1979 _journal_page_first 1541 _journal_page_last 1544 _publ_section_title ; Isomorph in melilites: refining of crystal structure of akermanite and intermediate melilite ; _database_code_amcsd 0017812 _chemical_compound_source 'Capo di Bove, Italy' _chemical_formula_sum '(Ca1.96 Na.04) Mg.24 Al.66 Fe.12 Si1.3 O7' _cell_length_a 7.738 _cell_length_b 7.738 _cell_length_c 5.045 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 90 _cell_volume 302.078 _exptl_crystal_density_diffrn 2.840 _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 _atom_site_U_iso_or_equiv Ca 0.33690 0.16310 0.51120 0.98000 0.01608 Na 0.33690 0.16310 0.51120 0.02000 0.01608 MgT1 0.00000 0.00000 0.00000 0.24000 0.01089 AlT1 0.00000 0.00000 0.00000 0.04000 0.01089 FeT1 0.00000 0.00000 0.00000 0.12000 0.01089 SiT2 0.14330 0.35670 0.95380 0.65000 0.00975 AlT2 0.14330 0.35670 0.95380 0.31000 0.00975 O1 0.50000 0.00000 0.17980 1.00000 0.01684 O2 0.14090 0.35910 0.27300 1.00000 0.01621 O3 0.08510 0.17480 0.80170 1.00000 0.01748