data_global
_chemical_name_mineral 'Akermanite'
loop_
_publ_author_name
'Merlini M'
'Gemmi M'
'Hanfland M'
'Crichton W'
_journal_name_full 'American Mineralogist'
_journal_volume 94 
_journal_year 2009
_journal_page_first 704
_journal_page_last 709
_publ_section_title
;
 High-pressure behavior of akermanite and gehlenite and phase stability
 of the normal structures in melelites
 Note: P = 15 GPa
;
_database_code_amcsd 0004934
_chemical_compound_source 'Synthetic'
_chemical_formula_sum 'Mg Ca2 Si2 O7'
_cell_length_a 7.570
_cell_length_b 7.570
_cell_length_c 4.781
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 273.975
_exptl_crystal_density_diffrn      3.305
_symmetry_space_group_name_H-M 'P -4 21 m'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2-y,1/2-x,z'
  'y,-x,-z'
  '1/2-x,1/2+y,-z'
  '-x,-y,z'
  '1/2+y,1/2+x,z'
  '-y,x,-z'
  '1/2+x,1/2-y,-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
Mg   0.00000   0.00000   0.00000
Ca   0.33710   0.16290   0.50420
Si   0.14300   0.35700   0.93920
O1   0.00000   0.50000  -0.19800
O2   0.14210   0.35790   0.26800
O3   0.08070   0.18410   0.77400