data_global
_chemical_name_mineral 'Pyroxene-ideal'
loop_
_publ_author_name
'Thompson R M'
'Downs R T'
_journal_name_full 'American Mineralogist'
_journal_volume 89 
_journal_year 2004
_journal_page_first 614
_journal_page_last 628
_publ_section_title
;
 Model pyroxenes II: Structural variation as a function of tetrahedral rotation
 model with O3-O3-O3 angle = 200 and model oxygen radius = 1
 Note: Atoms Mg, Si, and O are assigned to atomic positions for convenience
;
_database_code_amcsd 0003473
_chemical_formula_sum 'Mg Si O3'
_cell_length_a 7.608
_cell_length_b 6.823
_cell_length_c 3.939
_cell_angle_alpha 90
_cell_angle_beta 113.4
_cell_angle_gamma 90
_cell_volume 187.654
_exptl_crystal_density_diffrn      7.107
_symmetry_space_group_name_H-M 'C 1 2/c 1'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2+x,1/2+y,z'
  'x,-y,1/2+z'
  '1/2+x,1/2-y,1/2+z'
  '-x,y,1/2-z'
  '1/2-x,1/2+y,1/2-z'
  '-x,-y,-z'
  '1/2-x,1/2-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
Mg1   0.00000   0.91667   0.25000
Mg2   0.00000   0.25000   0.25000
Si   0.30850   0.08333   0.32040
O1   0.13300   0.08333   0.18560
O2   0.36700   0.25000   0.31440
O3   0.36700  -0.02550   0.14080