data_global
_chemical_name_mineral 'Akermanite'
loop_
_publ_author_name
'Swainson I P'
'Dove M T'
'Schmahl W W'
'Putnis A'
_journal_name_full 'Physics and Chemistry of Minerals'
_journal_volume 19 
_journal_year 1992
_journal_page_first 185
_journal_page_last 195
_publ_section_title
;
 Neutron powder diffraction study of the akermanite-gehlenite
 solid solution series
 Sample: 100% Ak
;
_database_code_amcsd 0007698
_chemical_formula_sum 'Ca2 Mg.96 Si2 O7'
_cell_length_a 7.8288
_cell_length_b 7.8288
_cell_length_c 5.0052
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 306.769
_exptl_crystal_density_diffrn      2.941
_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
Ca   0.33200   0.16800   0.50500   1.00000
MgT1   0.00000   0.00000   0.00000   0.96000
SiT2   0.13950   0.36050   0.93340   1.00000
O1   0.50000   0.00000   0.17750   1.00000
O2   0.14090   0.35910   0.25470   1.00000
O3   0.08160   0.18700   0.78790   1.00000
loop_
_atom_site_aniso_label
_atom_site_aniso_U_11
_atom_site_aniso_U_22
_atom_site_aniso_U_33
_atom_site_aniso_U_12
_atom_site_aniso_U_13
_atom_site_aniso_U_23
Ca 0.03394 0.03394 0.00797 0.01456 -0.00709 -0.00709
MgT1 0.01860 0.01860 0.02000 0.00000 0.00000 0.00000
SiT2 0.00605 0.00605 -0.00025 0.00062 -0.00189 -0.00189
O1 0.03139 0.03139 0.00367 -0.02695 0.00000 0.00000
O2 0.03127 0.03127 0.00506 0.00000 0.01380 0.01380
O3 0.05052 0.01379 0.01595 -0.01025 0.01062 -0.00544