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 #9b based on stacking sequence ABABCBAC
 Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
;
_database_code_amcsd 0003007
_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 1 21/c 1'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  'x,1/2-y,1/2+z'
  '-x,1/2+y,1/2-z'
  '-x,-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
SiA   0.96875   0.16667   0.33333
Mg1a   0.87500   0.66667   0.50000
Mg2a   0.87500   0.00000   0.50000
SiB   0.28125   0.33333   0.16667
SiC   0.21875   0.66667   0.50000
SiD   0.46875   0.16667   0.33333
Mg1b   0.37500   0.66667   0.83333
Mg2b   0.37500   0.00000   0.83333
O1A   0.06250   0.16667   0.33333
O2A   0.93750   0.00000   0.16667
O3A   0.93750   0.33333   0.16667
O1B   0.18750   0.33333   0.16667
O2B   0.31250   0.50000   0.00000
O3B   0.31250   0.33333   0.50000
O1C   0.31250   0.66667   0.50000
O2C   0.18750   0.50000   0.66667
O3C   0.18750   0.66667   0.16667
O1D   0.56250   0.16667   0.33333
O2D   0.43750   0.00000   0.16667
O3D   0.43750   0.33333   0.16667