The material structure described by CaAl2Si4O12 crystallizes in the monoclinic C2/c space group. Ca(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms to form CaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and corners with six equivalent Si(2)O4 tetrahedra. Al(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form distorted AlO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with three equivalent Al(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-68°. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-68°. There are six inequivalent O sites. In the first O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Si(1), and one Si(2) atom. In the second O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the third O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Al(1) and one Si(1) atom. In the fourth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Al(1) and one Si(2) atom. In the fifth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Si(1), and one Si(2) atom. In the sixth O site, O(1) is bonded in an L-shaped geometry to two equivalent Al(1) atoms. is represented by the CIF card [CIF]
data_CaAl2(SiO3)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.118
_cell_length_b   5.100
_cell_length_c   18.695
_cell_angle_alpha   87.420
_cell_angle_beta   84.853
_cell_angle_gamma   59.886
_symmetry_Int_Tables_number   1
_cell_volume   420.430
_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  0.100  0.800  0.750  1.0
  Ca  Ca1  1  0.900  0.200  0.250  1.0
  Al  Al2  1  0.295  0.853  0.999  1.0
  Al  Al3  1  0.705  0.147  0.001  1.0
  Al  Al4  1  0.852  0.853  0.501  1.0
  Al  Al5  1  0.148  0.147  0.499  1.0
  Si  Si6  1  0.720  0.469  0.863  1.0
  Si  Si7  1  0.280  0.531  0.137  1.0
  Si  Si8  1  0.811  0.469  0.637  1.0
  Si  Si9  1  0.189  0.531  0.363  1.0
  Si  Si10  1  0.474  0.138  0.638  1.0
  Si  Si11  1  0.526  0.862  0.362  1.0
  Si  Si12  1  0.387  0.138  0.862  1.0
  Si  Si13  1  0.613  0.862  0.138  1.0
  O  O14  1  0.042  0.937  0.568  1.0
  O  O15  1  0.958  0.063  0.432  1.0
  O  O16  1  0.020  0.937  0.932  1.0
  O  O17  1  0.980  0.063  0.068  1.0
  O  O18  1  0.549  0.388  0.673  1.0
  O  O19  1  0.451  0.612  0.327  1.0
  O  O20  1  0.063  0.388  0.827  1.0
  O  O21  1  0.937  0.612  0.173  1.0
  O  O22  1  0.623  0.251  0.821  1.0
  O  O23  1  0.377  0.749  0.179  1.0
  O  O24  1  0.126  0.251  0.679  1.0
  O  O25  1  0.874  0.749  0.321  1.0
  O  O26  1  0.639  0.520  0.947  1.0
  O  O27  1  0.361  0.480  0.053  1.0
  O  O28  1  0.841  0.520  0.553  1.0
  O  O29  1  0.159  0.480  0.447  1.0
  O  O30  1  0.461  0.140  0.554  1.0
  O  O31  1  0.539  0.860  0.446  1.0
  O  O32  1  0.399  0.140  0.946  1.0
  O  O33  1  0.601  0.860  0.054  1.0
  O  O34  1  0.506  0.807  0.822  1.0
  O  O35  1  0.494  0.193  0.178  1.0
  O  O36  1  0.687  0.807  0.678  1.0
  O  O37  1  0.313  0.193  0.322  1.0
[/CIF]
.
The material structure described by CaAl2Si4O12 crystallizes in the monoclinic C2/c space group. Ca(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms to form CaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and corners with six equivalent Si(2)O4 tetrahedra. Al(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form distorted AlO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with three equivalent Al(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-68°. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with three equivalent Ca(1)O6 octahedra, and corners with three equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-68°. There are six inequivalent O sites. In the first O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Si(1), and one Si(2) atom. In the second O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the third O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Al(1) and one Si(1) atom. In the fourth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Al(1) and one Si(2) atom. In the fifth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Si(1), and one Si(2) atom. In the sixth O site, O(1) is bonded in an L-shaped geometry to two equivalent Al(1) atoms. is represented by the CIF card [CIF]
data_CaAl2(SiO3)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.118
_cell_length_b   5.100
_cell_length_c   18.695
_cell_angle_alpha   87.420
_cell_angle_beta   84.853
_cell_angle_gamma   59.886
_symmetry_Int_Tables_number   1
_cell_volume   420.430
_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  0.100  0.800  0.750  1.0
  Ca  Ca1  1  0.900  0.200  0.250  1.0
  Al  Al2  1  0.295  0.853  0.999  1.0
  Al  Al3  1  0.705  0.147  0.001  1.0
  Al  Al4  1  0.852  0.853  0.501  1.0
  Al  Al5  1  0.148  0.147  0.499  1.0
  Si  Si6  1  0.720  0.469  0.863  1.0
  Si  Si7  1  0.280  0.531  0.137  1.0
  Si  Si8  1  0.811  0.469  0.637  1.0
  Si  Si9  1  0.189  0.531  0.363  1.0
  Si  Si10  1  0.474  0.138  0.638  1.0
  Si  Si11  1  0.526  0.862  0.362  1.0
  Si  Si12  1  0.387  0.138  0.862  1.0
  Si  Si13  1  0.613  0.862  0.138  1.0
  O  O14  1  0.042  0.937  0.568  1.0
  O  O15  1  0.958  0.063  0.432  1.0
  O  O16  1  0.020  0.937  0.932  1.0
  O  O17  1  0.980  0.063  0.068  1.0
  O  O18  1  0.549  0.388  0.673  1.0
  O  O19  1  0.451  0.612  0.327  1.0
  O  O20  1  0.063  0.388  0.827  1.0
  O  O21  1  0.937  0.612  0.173  1.0
  O  O22  1  0.623  0.251  0.821  1.0
  O  O23  1  0.377  0.749  0.179  1.0
  O  O24  1  0.126  0.251  0.679  1.0
  O  O25  1  0.874  0.749  0.321  1.0
  O  O26  1  0.639  0.520  0.947  1.0
  O  O27  1  0.361  0.480  0.053  1.0
  O  O28  1  0.841  0.520  0.553  1.0
  O  O29  1  0.159  0.480  0.447  1.0
  O  O30  1  0.461  0.140  0.554  1.0
  O  O31  1  0.539  0.860  0.446  1.0
  O  O32  1  0.399  0.140  0.946  1.0
  O  O33  1  0.601  0.860  0.054  1.0
  O  O34  1  0.506  0.807  0.822  1.0
  O  O35  1  0.494  0.193  0.178  1.0
  O  O36  1  0.687  0.807  0.678  1.0
  O  O37  1  0.313  0.193  0.322  1.0
[/CIF]
.