data_global _chemical_name_mineral 'Combeite' loop_ _publ_author_name 'Fischer R X' 'Tillmanns E' _journal_name_full 'Neues Jahrbuch fur Mineralogie, Monatshefte' _journal_volume 1983 _journal_year 1983 _journal_page_first 49 _journal_page_last 59 _publ_section_title ; Die Kristallstrukturen von naturlichem Na2Ca2Si3O9 vom Mt.Shaheru (Zaire) und aus dem Mayener Feld (Eifel) Note: this is the high-temperature form of combeite ; _database_code_amcsd 0019535 _chemical_compound_source 'Mt. Shaheru, Zaire' _chemical_formula_sum 'Na4 Ca4 Si6 O18' _cell_length_a 10.429 _cell_length_b 10.429 _cell_length_c 13.149 _cell_angle_alpha 90 _cell_angle_beta 90 _cell_angle_gamma 120 _cell_volume 1238.536 _exptl_crystal_density_diffrn 2.851 _symmetry_space_group_name_H-M 'R -3 m' loop_ _space_group_symop_operation_xyz 'x,y,z' '2/3+x,1/3+y,1/3+z' '1/3+x,2/3+y,2/3+z' 'x,x-y,z' '2/3+x,1/3+x-y,1/3+z' '1/3+x,2/3+x-y,2/3+z' 'y,x,-z' '2/3+y,1/3+x,1/3-z' '1/3+y,2/3+x,2/3-z' '-x+y,y,z' '2/3-x+y,1/3+y,1/3+z' '1/3-x+y,2/3+y,2/3+z' '-x,-x+y,-z' '2/3-x,1/3-x+y,1/3-z' '1/3-x,2/3-x+y,2/3-z' '-y,-x,z' '2/3-y,1/3-x,1/3+z' '1/3-y,2/3-x,2/3+z' 'x-y,-y,-z' '2/3+x-y,1/3-y,1/3-z' '1/3+x-y,2/3-y,2/3-z' 'y,-x+y,-z' '2/3+y,1/3-x+y,1/3-z' '1/3+y,2/3-x+y,2/3-z' '-x+y,-x,z' '2/3-x+y,1/3-x,1/3+z' '1/3-x+y,2/3-x,2/3+z' '-x,-y,-z' '2/3-x,1/3-y,1/3-z' '1/3-x,2/3-y,2/3-z' '-y,x-y,z' '2/3-y,1/3+x-y,1/3+z' '1/3-y,2/3+x-y,2/3+z' 'x-y,x,-z' '2/3+x-y,1/3+x,1/3-z' '1/3+x-y,2/3+x,2/3-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 Na1 0.50000 0.00000 0.00000 1.00000 0.02660 Na2 0.00000 0.00000 0.25040 0.50000 0.01001 Ca1 0.50000 0.00000 0.50000 1.00000 0.02546 Ca2 0.00000 0.00000 0.00000 1.00000 0.00684 Si 0.84900 0.69800 0.43580 1.00000 0.01381 O1 0.25240 0.00000 0.50000 1.00000 0.04433 O2 0.76110 0.52220 0.44540 1.00000 0.03420 O3 0.88500 0.77000 0.32600 1.00000 0.03040