data_global
_chemical_name_mineral 'Akermanite'
loop_
_publ_author_name
'Mokeeva V'
'Makarov E'
_journal_name_full 'Geokhimiya'
_journal_volume 10 
_journal_year 1979
_journal_page_first 1541
_journal_page_last 1544
_publ_section_title
;
 Isomorph in melilites: refining of crystal structure
 of akermanite and intermediate melilite
;
_database_code_amcsd 0017811
_chemical_compound_source 'Capo di Bove, Italy'
_chemical_formula_sum '(Ca1.5 Na.5) Mg.39 Al.41 Fe.16 Si2 O7'
_cell_length_a 7.760
_cell_length_b 7.760
_cell_length_c 5.029
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 302.834
_exptl_crystal_density_diffrn      2.953
_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
_atom_site_occupancy
_atom_site_U_iso_or_equiv
Ca   0.33580   0.16420   0.50910   0.75000   0.01520
Na   0.33580   0.16420   0.50910   0.25000   0.01520
MgT1   0.00000   0.00000   0.00000   0.39000   0.00861
AlT1   0.00000   0.00000   0.00000   0.41000   0.00861
FeT1   0.00000   0.00000   0.00000   0.16000   0.00861
SiT2   0.14060   0.35940   0.94160   1.00000   0.00785
O1   0.50000   0.00000   0.17750   1.00000   0.01583
O2   0.14140   0.35860   0.26040   1.00000   0.01735
O3   0.08330   0.18330   0.79850   1.00000   0.01798