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 #7 based on stacking sequence ABABACAC
 Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
;
_database_code_amcsd 0003003
_chemical_formula_sum 'Si Mg O3'
_cell_length_a 13.063945
_cell_length_b 6
_cell_length_c 3.4641016
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 271.529
_exptl_crystal_density_diffrn      9.823
_symmetry_space_group_name_H-M 'P 21 c a'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  'x,-y,1/2+z'
  '1/2+x,y,1/2-z'
  '1/2+x,-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
SiA   0.96875   0.91667   0.91667
SiB   0.90625   0.41667   0.75000
Mg1a   0.31250   0.08333   0.41667
Mg2a   0.31250   0.75000   0.41667
SiC   0.15625   0.08333   0.75000
SiD   0.21875   0.41667   0.08333
Mg1b   0.06250   0.41667   0.41667
Mg2b   0.06250   0.25000   0.91667
O1A   0.87500   0.91667   0.91667
O2A   0.00000   0.75000   0.75000
O3A   0.00000   0.08333   0.75000
O1B   0.00000   0.41667   0.75000
O2B   0.87500   0.58333   0.91667
O3B   0.87500   0.75000   0.41667
O1C   0.25000   0.08333   0.75000
O2C   0.12500   0.75000   0.08333
O3C   0.12500   0.08333   0.08333
O1D   0.12500   0.41667   0.08333
O2D   0.25000   0.25000   0.25000
O3D   0.25000   0.41667   0.75000