The material described by CaAl2SiO6 is Esseneite-like structured and crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form AlO4 tetrahedra that share  a cornercorner with one Al(3)O6 octahedra, corners with two equivalent Al(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-62°. In the second Al site, Al(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form AlO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Al(1)O4 tetrahedra, and edges with two equivalent Al(3)O6 octahedra. In the third Al site, Al(3) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form AlO6 octahedra that share corners with two equivalent Al(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Al(2)O6 octahedra. Si(1) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O6 octahedra, corners with two equivalent Al(3)O6 octahedra, and corners with two equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-60°. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Al(1), one Al(2), and one Al(3) atom to form a mixture of distorted corner and edge-sharing OCaAl3 tetrahedra. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(1), and one Al(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(2), one Al(2), one Al(3), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(3), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaAl2SiO6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.530
_cell_length_b   6.530
_cell_length_c   5.337
_cell_angle_alpha   78.099
_cell_angle_beta   78.099
_cell_angle_gamma   83.795
_symmetry_Int_Tables_number   1
_cell_volume   217.390
_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  0.689  0.311  0.000  1.0
  Ca  Ca1  1  0.311  0.689  0.500  1.0
  Al  Al2  1  0.616  0.814  0.961  1.0
  Al  Al3  1  0.186  0.384  0.039  1.0
  Al  Al4  1  0.091  0.909  0.000  1.0
  Al  Al5  1  0.909  0.091  0.500  1.0
  Si  Si6  1  0.386  0.195  0.534  1.0
  Si  Si7  1  0.805  0.614  0.466  1.0
  O  O8  1  0.822  0.987  0.862  1.0
  O  O9  1  0.358  0.898  0.071  1.0
  O  O10  1  0.630  0.658  0.724  1.0
  O  O11  1  0.013  0.178  0.138  1.0
  O  O12  1  0.102  0.642  0.929  1.0
  O  O13  1  0.342  0.370  0.276  1.0
  O  O14  1  0.195  0.031  0.618  1.0
  O  O15  1  0.625  0.098  0.446  1.0
  O  O16  1  0.378  0.329  0.764  1.0
  O  O17  1  0.969  0.805  0.382  1.0
  O  O18  1  0.902  0.375  0.554  1.0
  O  O19  1  0.671  0.622  0.236  1.0
[/CIF]
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The material described by CaAl2SiO6 is Esseneite-like structured and crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form AlO4 tetrahedra that share  a cornercorner with one Al(3)O6 octahedra, corners with two equivalent Al(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-62°. In the second Al site, Al(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form AlO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Al(1)O4 tetrahedra, and edges with two equivalent Al(3)O6 octahedra. In the third Al site, Al(3) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form AlO6 octahedra that share corners with two equivalent Al(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Al(2)O6 octahedra. Si(1) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O6 octahedra, corners with two equivalent Al(3)O6 octahedra, and corners with two equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-60°. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Al(1), one Al(2), and one Al(3) atom to form a mixture of distorted corner and edge-sharing OCaAl3 tetrahedra. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Ca(2), one Al(1), and one Al(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(2), one Al(2), one Al(3), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Al(3), and one Si(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Al(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaAl2SiO6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.530
_cell_length_b   6.530
_cell_length_c   5.337
_cell_angle_alpha   78.099
_cell_angle_beta   78.099
_cell_angle_gamma   83.795
_symmetry_Int_Tables_number   1
_cell_volume   217.390
_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  0.689  0.311  0.000  1.0
  Ca  Ca1  1  0.311  0.689  0.500  1.0
  Al  Al2  1  0.616  0.814  0.961  1.0
  Al  Al3  1  0.186  0.384  0.039  1.0
  Al  Al4  1  0.091  0.909  0.000  1.0
  Al  Al5  1  0.909  0.091  0.500  1.0
  Si  Si6  1  0.386  0.195  0.534  1.0
  Si  Si7  1  0.805  0.614  0.466  1.0
  O  O8  1  0.822  0.987  0.862  1.0
  O  O9  1  0.358  0.898  0.071  1.0
  O  O10  1  0.630  0.658  0.724  1.0
  O  O11  1  0.013  0.178  0.138  1.0
  O  O12  1  0.102  0.642  0.929  1.0
  O  O13  1  0.342  0.370  0.276  1.0
  O  O14  1  0.195  0.031  0.618  1.0
  O  O15  1  0.625  0.098  0.446  1.0
  O  O16  1  0.378  0.329  0.764  1.0
  O  O17  1  0.969  0.805  0.382  1.0
  O  O18  1  0.902  0.375  0.554  1.0
  O  O19  1  0.671  0.622  0.236  1.0
[/CIF]
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