data_9002911
_publ_section_title
;Model pyroxenes I: Ideal pyroxene topologies Pyroxene #4 based on CCP
 stacking sequence ABCABCABCABC. Ideal analogue of HP-C2/c pyroxene and
 eight-coordinaSiEd Mg2-C2/c pyroxene. Note: Atoms Mg, Si, and O are assigned
 to atomic positions just for convenience.
;
_journal_name_full               'American Mineralogist'
_journal_page_first              653
_journal_page_last               666
_journal_volume                  88
_journal_year                    2003
_chemical_formula_structural     Mg2(Si2O6)
_chemical_formula_sum            'Mg O3 Si'
_chemical_name_mineral           Pyroxene-ideal
_space_group_IT_number           15
_symmetry_space_group_name_Hall  '-C 2yc'
_symmetry_space_group_name_H-M   'C 1 2/c 1'
_cell_angle_alpha                90
_cell_angle_beta                 100.024987862
_cell_angle_gamma                90
_cell_length_a                   6.63324958071
_cell_length_b                   6.0
_cell_length_c                   3.46410161514
_cell_volume                     135.765
_exptl_crystal_density_diffrn    9.823
_[local]_cod_chemical_formula_sum_orig 'Si Mg O3'
_cod_database_code               9002911
loop_
_symmetry_equiv_pos_as_xyz
x,y,z
1/2+x,1/2+y,z
x,-y,1/2+z
1/2+x,1/2-y,1/2+z
-x,y,1/2-z
1/2-x,1/2+y,1/2-z
-x,-y,-z
1/2-x,1/2-y,-z
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
Si 0.31250 0.08333 0.18750
Mg1 0.00000 0.91667 0.25000
Mg2 0.00000 0.25000 0.25000
O1 0.12500 0.08333 0.12500
O2 0.37500 0.25000 0.37500
O3 0.37500 0.08333 0.87500
