The compound described by CaAl2(SiO5)2 crystallizes in the monoclinic P2_1/m space group. Ca(1) is bonded in a 4-coordinate geometry to one O(1), one O(6), and two equivalent O(3) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form AlO6 octahedra that share corners with four equivalent Si(1)O5 trigonal bipyramids and edges with two equivalent Al(2)O6 octahedra. In the second Al site, Al(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form distorted AlO6 octahedra that share edges with two equivalent Al(1)O6 octahedra and edges with two equivalent Si(1)O5 trigonal bipyramids. Si(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form SiO5 trigonal bipyramids that share corners with two equivalent Al(1)O6 octahedra,  an edgeedge with one Al(2)O6 octahedra, and  an edgeedge with one Si(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 35-42°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted water-like geometry to one Al(2) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Al(1), one Al(2), and one O(4) atom. In the fifth O site, O(5) is bonded in a T-shaped geometry to one Al(1), one Al(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1) and two equivalent Si(1) atoms. is represented by the CIF card [CIF]
data_CaAl2(SiO5)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.987
_cell_length_b   4.762
_cell_length_c   5.118
_cell_angle_alpha   76.819
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   331.893
_cell_formula_units_Z   2
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  0.250  0.090  0.316  1.0
  Ca  Ca1  1  0.750  0.910  0.684  1.0
  Al  Al2  1  0.500  0.000  0.500  1.0
  Al  Al3  1  0.000  0.000  0.500  1.0
  Al  Al4  1  0.500  0.500  0.000  1.0
  Al  Al5  1  0.000  0.500  0.000  1.0
  Si  Si6  1  0.657  0.605  0.273  1.0
  Si  Si7  1  0.157  0.395  0.727  1.0
  Si  Si8  1  0.343  0.395  0.727  1.0
  Si  Si9  1  0.843  0.605  0.273  1.0
  O  O10  1  0.250  0.157  0.868  1.0
  O  O11  1  0.750  0.843  0.132  1.0
  O  O12  1  0.632  0.520  0.974  1.0
  O  O13  1  0.132  0.480  0.026  1.0
  O  O14  1  0.368  0.480  0.026  1.0
  O  O15  1  0.868  0.520  0.974  1.0
  O  O16  1  0.885  0.843  0.442  1.0
  O  O17  1  0.385  0.157  0.558  1.0
  O  O18  1  0.115  0.157  0.558  1.0
  O  O19  1  0.615  0.843  0.442  1.0
  O  O20  1  0.523  0.918  0.921  1.0
  O  O21  1  0.023  0.082  0.079  1.0
  O  O22  1  0.477  0.082  0.079  1.0
  O  O23  1  0.977  0.918  0.921  1.0
  O  O24  1  0.549  0.385  0.370  1.0
  O  O25  1  0.049  0.615  0.630  1.0
  O  O26  1  0.451  0.615  0.630  1.0
  O  O27  1  0.951  0.385  0.370  1.0
  O  O28  1  0.250  0.596  0.548  1.0
  O  O29  1  0.750  0.404  0.452  1.0
[/CIF]
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The compound described by CaAl2(SiO5)2 crystallizes in the monoclinic P2_1/m space group. Ca(1) is bonded in a 4-coordinate geometry to one O(1), one O(6), and two equivalent O(3) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form AlO6 octahedra that share corners with four equivalent Si(1)O5 trigonal bipyramids and edges with two equivalent Al(2)O6 octahedra. In the second Al site, Al(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form distorted AlO6 octahedra that share edges with two equivalent Al(1)O6 octahedra and edges with two equivalent Si(1)O5 trigonal bipyramids. Si(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form SiO5 trigonal bipyramids that share corners with two equivalent Al(1)O6 octahedra,  an edgeedge with one Al(2)O6 octahedra, and  an edgeedge with one Si(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 35-42°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted water-like geometry to one Al(2) and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Al(1), one Al(2), and one O(4) atom. In the fifth O site, O(5) is bonded in a T-shaped geometry to one Al(1), one Al(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1) and two equivalent Si(1) atoms. is represented by the CIF card [CIF]
data_CaAl2(SiO5)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.987
_cell_length_b   4.762
_cell_length_c   5.118
_cell_angle_alpha   76.819
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   331.893
_cell_formula_units_Z   2
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  0.250  0.090  0.316  1.0
  Ca  Ca1  1  0.750  0.910  0.684  1.0
  Al  Al2  1  0.500  0.000  0.500  1.0
  Al  Al3  1  0.000  0.000  0.500  1.0
  Al  Al4  1  0.500  0.500  0.000  1.0
  Al  Al5  1  0.000  0.500  0.000  1.0
  Si  Si6  1  0.657  0.605  0.273  1.0
  Si  Si7  1  0.157  0.395  0.727  1.0
  Si  Si8  1  0.343  0.395  0.727  1.0
  Si  Si9  1  0.843  0.605  0.273  1.0
  O  O10  1  0.250  0.157  0.868  1.0
  O  O11  1  0.750  0.843  0.132  1.0
  O  O12  1  0.632  0.520  0.974  1.0
  O  O13  1  0.132  0.480  0.026  1.0
  O  O14  1  0.368  0.480  0.026  1.0
  O  O15  1  0.868  0.520  0.974  1.0
  O  O16  1  0.885  0.843  0.442  1.0
  O  O17  1  0.385  0.157  0.558  1.0
  O  O18  1  0.115  0.157  0.558  1.0
  O  O19  1  0.615  0.843  0.442  1.0
  O  O20  1  0.523  0.918  0.921  1.0
  O  O21  1  0.023  0.082  0.079  1.0
  O  O22  1  0.477  0.082  0.079  1.0
  O  O23  1  0.977  0.918  0.921  1.0
  O  O24  1  0.549  0.385  0.370  1.0
  O  O25  1  0.049  0.615  0.630  1.0
  O  O26  1  0.451  0.615  0.630  1.0
  O  O27  1  0.951  0.385  0.370  1.0
  O  O28  1  0.250  0.596  0.548  1.0
  O  O29  1  0.750  0.404  0.452  1.0
[/CIF]
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