data_Ca2Al2SiO7
_cell_length_a                   7.716
_cell_length_b                   7.716
_cell_length_c                   5.089
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_volume                     302.982
_symmetry_space_group_name_H-M   'P -4 21 m'
_symmetry_int_tables_number      113
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_type_symbol
_atom_type_oxidation_number
  Ca1  +2
  AlT1 +3
  AlT2 +3
  SiT2 +4
  O1   -2
  O2   -2
  O3   -2
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
Ca1   0.33750 0.16250 0.51100 1.00000
AlT1  0.00000 0.00000 0.00000 1.00000
AlT2  0.14310 0.35690 0.95280 0.50000
SiT2  0.14310 0.35690 0.95280 0.50000
O1    0.50000 0.00000 0.18840 1.00000
O2    0.14180 0.35820 0.28320 1.00000
O3    0.08720 0.17060 0.80330 1.00000