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 kosmochlor after Cameron et al. (1973)
 with O3-O3-O3 angle = 172.0 and model oxygen radius = 1.294
;
_database_code_amcsd 0003483
_chemical_formula_sum 'Cr Na Si2 O6'
_cell_length_a 9.653
_cell_length_b 8.944
_cell_length_c 5.164
_cell_angle_alpha 90
_cell_angle_beta 109.6
_cell_angle_gamma 90
_cell_volume 420.008
_exptl_crystal_density_diffrn      3.592
_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
Cr   0.00000   0.91667   0.25000
Na   0.00000   0.25000   0.25000
Si   0.30810   0.08333   0.27630
O1   0.13380   0.08333   0.16720
O2   0.36620   0.25000   0.33280
O3   0.36620   0.01000   0.05270