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 #2 based on stacking sequence ABAC. Ideal analogue of  protopyroxene,
 high-P protopyroxene.
 Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
;
_database_code_amcsd 0002997
_chemical_formula_sum 'Mg Si O3'
_cell_length_a 6.5319726
_cell_length_b 6
_cell_length_c 3.4641016
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 135.764
_exptl_crystal_density_diffrn      9.823
_symmetry_space_group_name_H-M 'P 21 c n'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  'x,-y,1/2+z'
  '1/2+x,1/2+y,1/2-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   0.08333   0.66667
Mg2   0.00000   0.25000   0.16667
SiA   0.68750   0.91667   0.83333
SiB   0.31250   0.08333   0.00000
O1A   0.87500   0.91667   0.83333
O1B   0.12500   0.08333   0.00000
O2A   0.62500   0.75000   0.00000
O2B   0.37500   0.25000   0.16667
O3A   0.62500   0.91667   0.50000
O3B   0.37500   0.91667   0.16667