The compound described by CaAl2Si2O8 crystallizes in the trigonal P-3c1 space group. Ca(1) is bonded to six equivalent O(1) atoms to form CaO6 octahedra that share corners with six equivalent Al(1)O4 tetrahedra and corners with six equivalent Si(1)O4 tetrahedra. Al(1) is bonded to one O(2) and three equivalent O(1) atoms to form AlO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 62°. Si(1) is bonded to one O(2) and three equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and corners with four equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 59°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Ca(1), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a linear geometry to one Al(1) and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaAl2(SiO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.152
_cell_length_b   5.152
_cell_length_c   14.990
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   344.588
_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  0.000  0.000  0.500  1.0
  Ca  Ca1  1  0.000  0.000  0.000  1.0
  Al  Al2  1  0.667  0.667  0.642  1.0
  Al  Al3  1  0.333  0.333  0.358  1.0
  Al  Al4  1  0.667  0.667  0.142  1.0
  Al  Al5  1  0.333  0.333  0.858  1.0
  Si  Si6  1  0.333  0.333  0.637  1.0
  Si  Si7  1  0.667  0.667  0.363  1.0
  Si  Si8  1  0.333  0.333  0.137  1.0
  Si  Si9  1  0.667  0.667  0.863  1.0
  O  O10  1  0.377  0.013  0.598  1.0
  O  O11  1  0.013  0.610  0.598  1.0
  O  O12  1  0.610  0.377  0.598  1.0
  O  O13  1  0.623  0.987  0.402  1.0
  O  O14  1  0.987  0.390  0.402  1.0
  O  O15  1  0.390  0.623  0.402  1.0
  O  O16  1  0.610  0.013  0.098  1.0
  O  O17  1  0.013  0.377  0.098  1.0
  O  O18  1  0.377  0.610  0.098  1.0
  O  O19  1  0.390  0.987  0.902  1.0
  O  O20  1  0.987  0.623  0.902  1.0
  O  O21  1  0.623  0.390  0.902  1.0
  O  O22  1  0.667  0.667  0.757  1.0
  O  O23  1  0.333  0.333  0.743  1.0
  O  O24  1  0.333  0.333  0.243  1.0
  O  O25  1  0.667  0.667  0.257  1.0
[/CIF]
.
The compound described by CaAl2Si2O8 crystallizes in the trigonal P-3c1 space group. Ca(1) is bonded to six equivalent O(1) atoms to form CaO6 octahedra that share corners with six equivalent Al(1)O4 tetrahedra and corners with six equivalent Si(1)O4 tetrahedra. Al(1) is bonded to one O(2) and three equivalent O(1) atoms to form AlO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 62°. Si(1) is bonded to one O(2) and three equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and corners with four equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 59°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Ca(1), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a linear geometry to one Al(1) and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaAl2(SiO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.152
_cell_length_b   5.152
_cell_length_c   14.990
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   344.588
_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  0.000  0.000  0.500  1.0
  Ca  Ca1  1  0.000  0.000  0.000  1.0
  Al  Al2  1  0.667  0.667  0.642  1.0
  Al  Al3  1  0.333  0.333  0.358  1.0
  Al  Al4  1  0.667  0.667  0.142  1.0
  Al  Al5  1  0.333  0.333  0.858  1.0
  Si  Si6  1  0.333  0.333  0.637  1.0
  Si  Si7  1  0.667  0.667  0.363  1.0
  Si  Si8  1  0.333  0.333  0.137  1.0
  Si  Si9  1  0.667  0.667  0.863  1.0
  O  O10  1  0.377  0.013  0.598  1.0
  O  O11  1  0.013  0.610  0.598  1.0
  O  O12  1  0.610  0.377  0.598  1.0
  O  O13  1  0.623  0.987  0.402  1.0
  O  O14  1  0.987  0.390  0.402  1.0
  O  O15  1  0.390  0.623  0.402  1.0
  O  O16  1  0.610  0.013  0.098  1.0
  O  O17  1  0.013  0.377  0.098  1.0
  O  O18  1  0.377  0.610  0.098  1.0
  O  O19  1  0.390  0.987  0.902  1.0
  O  O20  1  0.987  0.623  0.902  1.0
  O  O21  1  0.623  0.390  0.902  1.0
  O  O22  1  0.667  0.667  0.757  1.0
  O  O23  1  0.333  0.333  0.743  1.0
  O  O24  1  0.333  0.333  0.243  1.0
  O  O25  1  0.667  0.667  0.257  1.0
[/CIF]
.