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 = 15.7 GPa
;
_database_code_amcsd 0004935
_chemical_compound_source 'Synthetic'
_chemical_formula_sum 'Mg Si2 Ca2 O7'
_cell_length_a 8.82
_cell_length_b 7.34
_cell_length_c 9.13
_cell_angle_alpha 90
_cell_angle_beta 115.1
_cell_angle_gamma 90
_cell_volume 535.250
_exptl_crystal_density_diffrn      3.383
_symmetry_space_group_name_H-M 'P 1 21/n 1'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2+x,1/2-y,1/2+z'
  '1/2-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
Mg   0.81070   0.09970   0.09260
Si1   0.86480   0.45120   0.21500
Si2   0.95750   0.75540   0.07310
Ca1   0.45930   0.27940   0.02940
Ca2   0.30280   0.56380   0.21210
O1   0.99750   0.56180   0.15930
O2   0.88010   0.52210   0.37910
O3   0.69800   0.47280   0.04100
O4   0.00490   0.88000   0.22570
O5   0.12630   0.82080   0.06620
O6   0.95300   0.26250   0.28560
O7   0.78300   0.75830  -0.09700