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 #3a based on stacking sequence ABABCACABCBC
 Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
;
_database_code_amcsd 0002998
_chemical_formula_sum 'Si Mg O3'
_cell_length_a 6.6332495
_cell_length_b 6
_cell_length_c 3.4641016
_cell_angle_alpha 90
_cell_angle_beta 100.0250
_cell_angle_gamma 90
_cell_volume 135.764
_exptl_crystal_density_diffrn      9.823
_symmetry_space_group_name_H-M 'P 1 2/c 1'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  'x,-y,1/2+z'
  '-x,y,1/2-z'
  '-x,-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
SiA   0.68750   0.58333   0.31250
SiB   0.81250   0.91667   0.02083
Mg1a   0.00000   0.58333   0.75000
Mg2a   0.00000   0.25000   0.75000
Mg1b   0.50000   0.08333   0.75000
Mg2b   0.50000   0.75000   0.75000
O1A   0.87500   0.58333   0.37500
O2A   0.62500   0.75000   0.45833
O3A   0.62500   0.41667   0.45833
O1B   0.62500   0.08333   0.45833
O2B   0.87500   0.25000   0.37500
O3B   0.87500   0.91667   0.37500