data_global _chemical_name_mineral 'Beta-diopside' loop_ _publ_author_name 'Plonka A M' 'Dera P' 'Irmen P' 'Rivers M L' 'Ehm L' 'Parise J B' _journal_name_full 'Geophysical Research Letters' _journal_volume 39 _journal_year 2012 _journal_page_first _journal_page_last L24307 _publ_section_title ; Beta-diopside, a new ultrahigh-pressure polymorph of CaMgSi2O6 with six-coordinated silicon Note: P = 56.1 GPa ; _database_code_amcsd 0020131 _chemical_compound_source 'synthesize from natural sample' _chemical_formula_sum 'Ca Mg Si2 O6' _cell_length_a 9.053 _cell_length_b 7.677 _cell_length_c 4.751 _cell_angle_alpha 90 _cell_angle_beta 96.34 _cell_angle_gamma 90 _cell_volume 328.174 _exptl_crystal_density_diffrn 4.383 _symmetry_space_group_name_H-M 'P 1 21/c 1' loop_ _space_group_symop_operation_xyz 'x,y,z' 'x,1/2-y,1/2+z' '-x,1/2+y,1/2-z' '-x,-y,-z' loop_ _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv Ca(1) 0.73930 0.06750 0.09010 0.00600 Mg(1) 0.24200 0.16410 0.40320 0.00300 Si(1) 0.51080 0.16600 0.46270 0.00600 Si(2) 0.03160 0.85430 0.26340 0.00800 O(1) 0.39370 0.16930 0.11290 0.00500 O(2) 0.39130 0.48310 0.08570 0.00400 O(3) 0.61540 0.29320 0.26730 0.00400 O(4) 0.14250 0.35160 0.21680 0.00500 O(5) 0.10560 0.02890 0.19830 0.00900 O(6) 0.10820 0.70900 0.06950 0.00700