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 #3b based on stacking sequence ABABCACABCBC. Ideal analogue of low
 clinopyroxene.
 Note: Atoms Mg, Si, and O are assigned to atomic positions just for convenience.
;
_database_code_amcsd 0002999
_chemical_formula_sum 'Si Mg O3'
_cell_length_a 6.9282032
_cell_length_b 6
_cell_length_c 3.4641016
_cell_angle_alpha 90
_cell_angle_beta 109.4712
_cell_angle_gamma 90
_cell_volume 135.765
_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   0.06250   0.33333   0.37500
SiB   0.56250   0.83333   0.20833
Mg1   0.25000   0.66667   0.16667
Mg2   0.25000   0.00000   0.16667
O1A   0.87500   0.33333   0.25000
O1B   0.37500   0.83333   0.08333
O2A   0.12500   0.50000   0.25000
O2B   0.62500   0.00000   0.41667
O3A   0.12500   0.33333   0.75000
O3B   0.62500   0.66667   0.41667