The material structure described by Ca2Al2SiO7 crystallizes in the orthorhombic P2_12_12_1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(7), and two equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and two equivalent O(3) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form distorted AlO4 trigonal pyramids that share corners with two equivalent Si(1)O4 tetrahedra,  a cornercorner with one Al(2)O5 trigonal bipyramid, and  an edgeedge with one Al(2)O5 trigonal bipyramid. In the second Al site, Al(2) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(7) atom to form AlO5 trigonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra,  a cornercorner with one Al(1)O4 trigonal pyramid, and  an edgeedge with one Al(1)O4 trigonal pyramid. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(2)O5 trigonal bipyramids and corners with two equivalent Al(1)O4 trigonal pyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(2), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Ca(2), one Al(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ca(2) and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Al(2) atom. In the fifth O site, O(5) is bonded to one Ca(2), two equivalent Ca(1), and one Al(2) atom to form distorted corner-sharing OCa3Al tetrahedra. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Al(1), one Al(2), and one Si(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(1), and one Al(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2Al2SiO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.963
_cell_length_b   6.083
_cell_length_c   7.736
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   657.096
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ca  Ca0  1  0.322  0.112  0.655  1.0
  Ca  Ca1  1  0.204  0.693  0.403  1.0
  Ca  Ca2  1  0.296  0.193  0.097  1.0
  Ca  Ca3  1  0.178  0.612  0.845  1.0
  Ca  Ca4  1  0.704  0.307  0.597  1.0
  Ca  Ca5  1  0.822  0.888  0.345  1.0
  Ca  Ca6  1  0.678  0.388  0.155  1.0
  Ca  Ca7  1  0.796  0.807  0.903  1.0
  Al  Al8  1  0.021  0.012  0.035  1.0
  Al  Al9  1  0.979  0.488  0.535  1.0
  Al  Al10  1  0.607  0.839  0.257  1.0
  Al  Al11  1  0.893  0.339  0.243  1.0
  Al  Al12  1  0.521  0.988  0.965  1.0
  Al  Al13  1  0.479  0.512  0.465  1.0
  Al  Al14  1  0.107  0.161  0.743  1.0
  Al  Al15  1  0.393  0.661  0.757  1.0
  Si  Si16  1  0.893  0.333  0.859  1.0
  Si  Si17  1  0.607  0.833  0.641  1.0
  Si  Si18  1  0.393  0.667  0.141  1.0
  Si  Si19  1  0.107  0.167  0.359  1.0
  O  O20  1  0.352  0.544  0.966  1.0
  O  O21  1  0.104  0.972  0.208  1.0
  O  O22  1  0.323  0.857  0.219  1.0
  O  O23  1  0.094  0.453  0.623  1.0
  O  O24  1  0.287  0.734  0.650  1.0
  O  O25  1  0.991  0.230  0.399  1.0
  O  O26  1  0.071  0.894  0.849  1.0
  O  O27  1  0.509  0.730  0.101  1.0
  O  O28  1  0.429  0.394  0.651  1.0
  O  O29  1  0.213  0.234  0.850  1.0
  O  O30  1  0.396  0.472  0.292  1.0
  O  O31  1  0.177  0.357  0.281  1.0
  O  O32  1  0.406  0.953  0.877  1.0
  O  O33  1  0.148  0.044  0.534  1.0
  O  O34  1  0.852  0.456  0.034  1.0
  O  O35  1  0.604  0.028  0.792  1.0
  O  O36  1  0.787  0.266  0.350  1.0
  O  O37  1  0.594  0.547  0.377  1.0
  O  O38  1  0.823  0.143  0.781  1.0
  O  O39  1  0.571  0.106  0.151  1.0
  O  O40  1  0.491  0.770  0.601  1.0
  O  O41  1  0.929  0.606  0.349  1.0
  O  O42  1  0.009  0.270  0.899  1.0
  O  O43  1  0.906  0.047  0.123  1.0
  O  O44  1  0.677  0.643  0.719  1.0
  O  O45  1  0.896  0.528  0.708  1.0
  O  O46  1  0.713  0.766  0.150  1.0
  O  O47  1  0.648  0.956  0.466  1.0
[/CIF]
.
The material structure described by Ca2Al2SiO7 crystallizes in the orthorhombic P2_12_12_1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(7), and two equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and two equivalent O(3) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form distorted AlO4 trigonal pyramids that share corners with two equivalent Si(1)O4 tetrahedra,  a cornercorner with one Al(2)O5 trigonal bipyramid, and  an edgeedge with one Al(2)O5 trigonal bipyramid. In the second Al site, Al(2) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(7) atom to form AlO5 trigonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra,  a cornercorner with one Al(1)O4 trigonal pyramid, and  an edgeedge with one Al(1)O4 trigonal pyramid. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(2)O5 trigonal bipyramids and corners with two equivalent Al(1)O4 trigonal pyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(2), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Ca(2), one Al(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ca(2) and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Al(2) atom. In the fifth O site, O(5) is bonded to one Ca(2), two equivalent Ca(1), and one Al(2) atom to form distorted corner-sharing OCa3Al tetrahedra. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Al(1), one Al(2), and one Si(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(1), and one Al(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca2Al2SiO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.963
_cell_length_b   6.083
_cell_length_c   7.736
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   657.096
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ca  Ca0  1  0.322  0.112  0.655  1.0
  Ca  Ca1  1  0.204  0.693  0.403  1.0
  Ca  Ca2  1  0.296  0.193  0.097  1.0
  Ca  Ca3  1  0.178  0.612  0.845  1.0
  Ca  Ca4  1  0.704  0.307  0.597  1.0
  Ca  Ca5  1  0.822  0.888  0.345  1.0
  Ca  Ca6  1  0.678  0.388  0.155  1.0
  Ca  Ca7  1  0.796  0.807  0.903  1.0
  Al  Al8  1  0.021  0.012  0.035  1.0
  Al  Al9  1  0.979  0.488  0.535  1.0
  Al  Al10  1  0.607  0.839  0.257  1.0
  Al  Al11  1  0.893  0.339  0.243  1.0
  Al  Al12  1  0.521  0.988  0.965  1.0
  Al  Al13  1  0.479  0.512  0.465  1.0
  Al  Al14  1  0.107  0.161  0.743  1.0
  Al  Al15  1  0.393  0.661  0.757  1.0
  Si  Si16  1  0.893  0.333  0.859  1.0
  Si  Si17  1  0.607  0.833  0.641  1.0
  Si  Si18  1  0.393  0.667  0.141  1.0
  Si  Si19  1  0.107  0.167  0.359  1.0
  O  O20  1  0.352  0.544  0.966  1.0
  O  O21  1  0.104  0.972  0.208  1.0
  O  O22  1  0.323  0.857  0.219  1.0
  O  O23  1  0.094  0.453  0.623  1.0
  O  O24  1  0.287  0.734  0.650  1.0
  O  O25  1  0.991  0.230  0.399  1.0
  O  O26  1  0.071  0.894  0.849  1.0
  O  O27  1  0.509  0.730  0.101  1.0
  O  O28  1  0.429  0.394  0.651  1.0
  O  O29  1  0.213  0.234  0.850  1.0
  O  O30  1  0.396  0.472  0.292  1.0
  O  O31  1  0.177  0.357  0.281  1.0
  O  O32  1  0.406  0.953  0.877  1.0
  O  O33  1  0.148  0.044  0.534  1.0
  O  O34  1  0.852  0.456  0.034  1.0
  O  O35  1  0.604  0.028  0.792  1.0
  O  O36  1  0.787  0.266  0.350  1.0
  O  O37  1  0.594  0.547  0.377  1.0
  O  O38  1  0.823  0.143  0.781  1.0
  O  O39  1  0.571  0.106  0.151  1.0
  O  O40  1  0.491  0.770  0.601  1.0
  O  O41  1  0.929  0.606  0.349  1.0
  O  O42  1  0.009  0.270  0.899  1.0
  O  O43  1  0.906  0.047  0.123  1.0
  O  O44  1  0.677  0.643  0.719  1.0
  O  O45  1  0.896  0.528  0.708  1.0
  O  O46  1  0.713  0.766  0.150  1.0
  O  O47  1  0.648  0.956  0.466  1.0
[/CIF]
.