data_global
_chemical_name_mineral 'Pyroxene-ideal'
loop_
_publ_author_name
'Thompson R M'
'Downs R T'
_journal_name_full 'American Mineralogist'
_journal_volume 88 
_journal_year 2003
_journal_page_first 653
_journal_page_last 666
_publ_section_title
;
 Model pyroxenes I: Ideal pyroxene topologies
 Pyroxene #1 based on HCP stacking sequence ABAB. Has the bonding topology of
 observed HT-C2/c pyroxenes.
 Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
;
_database_code_amcsd 0002996
_chemical_formula_sum 'Mg Si O3'
_cell_length_a 7.3936910
_cell_length_b 6
_cell_length_c 3.4641016
_cell_angle_alpha 90
_cell_angle_beta 117.9383
_cell_angle_gamma 90
_cell_volume 135.765
_exptl_crystal_density_diffrn      9.823
_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   0.31250   0.08333   0.39583
O1   0.12500   0.08333   0.20833
O2   0.37500   0.25000   0.29167
O3   0.37500   0.91667   0.29167