data_global _chemical_name_mineral 'Perrierite-(La)' loop_ _publ_author_name 'Calvo C' 'Faggiani R' _journal_name_full 'American Mineralogist' _journal_volume 59 _journal_year 1974 _journal_page_first 1277 _journal_page_last 1285 _publ_section_title ; A re-investigation of the crystal structures of chevkinite and perrierite ; _database_code_amcsd 435 _chemical_compound_source 'Synthetic' _chemical_formula_sum 'La4 Si4 Mg2 Ti3 O22' _cell_length_a 13.818 _cell_length_b 5.677 _cell_length_c 11.787 _cell_angle_alpha 90.0 _cell_angle_beta 113.85 _cell_angle_gamma 90.0 _cell_volume 845.672 _exptl_crystal_density_diffrn 4.76 _symmetry_space_group_name_H-M 'P 1 21/a 1' loop_ _space_group_symop_operation_xyz 'x,y,z' '1/2+x,1/2-y,z' '1/2-x,1/2+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 La1 0.23756 0.0198 0.26687 1.0 0.0078 La2 0.04897 0.0265 0.7432 1.0 0.0087 Si1 0.4123 -0.0001 0.7322 1.0 0.0057 Si2 0.1624 0.0027 0.5489 1.0 0.0069 Mg 0.0 0.5 0.5 1.0 0.0047 Ti1 -0.0039 0.2385 0.0004 0.616 0.0105 Mg1 -0.0039 0.2385 0.0004 0.384 0.0105 Ti2 0.2749 0.0071 0.017 0.884 0.0068 Mg2 0.2749 0.0071 0.017 0.116 0.0068 O1 0.0794 -0.2597 0.1864 1.0 0.0091 O11 0.0652 0.2556 0.1858 1.0 0.0103 O2 0.2899 0.2606 0.1229 1.0 0.0128 O21 0.2875 -0.2401 0.1225 1.0 0.0105 O3 0.3736 -0.2511 0.4058 1.0 0.0123 O31 0.392 0.2862 0.4066 1.0 0.0139 O4 0.0957 0.0077 0.9894 1.0 0.0114 O5 0.4067 -0.0041 0.0089 1.0 0.011 O6 0.4932 0.0328 0.666667 1.0 0.015 O7 0.2884 -0.0337 0.6366 1.0 0.0176 O8 0.1384 -0.0036 0.4042 1.0 0.0115