The structure described by CaAl2Si3O13 crystallizes in the monoclinic Cc space group. Ca(1) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(2), one O(3), one O(5), and one O(6) atom. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(10), one O(2), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(4), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Al(2)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(1), one O(2), one O(3), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Al(1) and one Si(3) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), and one Si(3) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Al(2), and one Si(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Al(2) and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1), one Al(2), and one Si(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(1) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one Ca(1) and one O(13) atom. In the twelfth O site, O(12) is bonded in a single-bond geometry to one Ca(1) atom. In the thirteenth O site, O(13) is bonded in a single-bond geometry to one O(11) atom. is represented by the CIF file [CIF]
data_CaAl2Si3O13
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.879
_cell_length_b   9.879
_cell_length_c   9.657
_cell_angle_alpha   84.383
_cell_angle_beta   84.383
_cell_angle_gamma   140.408
_symmetry_Int_Tables_number   1
_cell_volume   575.033
_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  0.206  0.022  0.440  1.0
  Ca  Ca1  1  0.022  0.206  0.940  1.0
  Al  Al2  1  0.189  0.628  0.411  1.0
  Al  Al3  1  0.628  0.189  0.911  1.0
  Al  Al4  1  0.376  0.315  0.059  1.0
  Al  Al5  1  0.315  0.376  0.559  1.0
  Si  Si6  1  0.646  0.885  0.484  1.0
  Si  Si7  1  0.885  0.646  0.984  1.0
  Si  Si8  1  0.126  0.303  0.289  1.0
  Si  Si9  1  0.303  0.126  0.789  1.0
  Si  Si10  1  0.222  0.891  0.171  1.0
  Si  Si11  1  0.891  0.222  0.671  1.0
  O  O12  1  0.417  0.966  0.065  1.0
  O  O13  1  0.966  0.417  0.565  1.0
  O  O14  1  0.169  0.784  0.341  1.0
  O  O15  1  0.784  0.169  0.841  1.0
  O  O16  1  0.290  0.104  0.186  1.0
  O  O17  1  0.104  0.290  0.686  1.0
  O  O18  1  0.662  0.567  0.025  1.0
  O  O19  1  0.567  0.662  0.525  1.0
  O  O20  1  0.206  0.320  0.123  1.0
  O  O21  1  0.320  0.206  0.623  1.0
  O  O22  1  0.240  0.292  0.397  1.0
  O  O23  1  0.292  0.240  0.897  1.0
  O  O24  1  0.859  0.060  0.340  1.0
  O  O25  1  0.060  0.859  0.840  1.0
  O  O26  1  0.180  0.503  0.289  1.0
  O  O27  1  0.503  0.180  0.789  1.0
  O  O28  1  0.993  0.719  0.121  1.0
  O  O29  1  0.719  0.993  0.621  1.0
  O  O30  1  0.439  0.808  0.457  1.0
  O  O31  1  0.808  0.439  0.957  1.0
  O  O32  1  0.662  0.258  0.328  1.0
  O  O33  1  0.258  0.662  0.828  1.0
  O  O34  1  0.706  0.816  0.056  1.0
  O  O35  1  0.816  0.706  0.556  1.0
  O  O36  1  0.744  0.240  0.240  1.0
  O  O37  1  0.240  0.744  0.740  1.0
[/CIF]
.
The structure described by CaAl2Si3O13 crystallizes in the monoclinic Cc space group. Ca(1) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(2), one O(3), one O(5), and one O(6) atom. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(10), one O(2), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(4), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Al(2)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(1), one O(2), one O(3), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Al(1) and one Si(3) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), and one Si(3) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Al(2), and one Si(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Al(2) and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1), one Al(2), and one Si(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(1) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one Ca(1) and one O(13) atom. In the twelfth O site, O(12) is bonded in a single-bond geometry to one Ca(1) atom. In the thirteenth O site, O(13) is bonded in a single-bond geometry to one O(11) atom. is represented by the CIF file [CIF]
data_CaAl2Si3O13
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.879
_cell_length_b   9.879
_cell_length_c   9.657
_cell_angle_alpha   84.383
_cell_angle_beta   84.383
_cell_angle_gamma   140.408
_symmetry_Int_Tables_number   1
_cell_volume   575.033
_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  0.206  0.022  0.440  1.0
  Ca  Ca1  1  0.022  0.206  0.940  1.0
  Al  Al2  1  0.189  0.628  0.411  1.0
  Al  Al3  1  0.628  0.189  0.911  1.0
  Al  Al4  1  0.376  0.315  0.059  1.0
  Al  Al5  1  0.315  0.376  0.559  1.0
  Si  Si6  1  0.646  0.885  0.484  1.0
  Si  Si7  1  0.885  0.646  0.984  1.0
  Si  Si8  1  0.126  0.303  0.289  1.0
  Si  Si9  1  0.303  0.126  0.789  1.0
  Si  Si10  1  0.222  0.891  0.171  1.0
  Si  Si11  1  0.891  0.222  0.671  1.0
  O  O12  1  0.417  0.966  0.065  1.0
  O  O13  1  0.966  0.417  0.565  1.0
  O  O14  1  0.169  0.784  0.341  1.0
  O  O15  1  0.784  0.169  0.841  1.0
  O  O16  1  0.290  0.104  0.186  1.0
  O  O17  1  0.104  0.290  0.686  1.0
  O  O18  1  0.662  0.567  0.025  1.0
  O  O19  1  0.567  0.662  0.525  1.0
  O  O20  1  0.206  0.320  0.123  1.0
  O  O21  1  0.320  0.206  0.623  1.0
  O  O22  1  0.240  0.292  0.397  1.0
  O  O23  1  0.292  0.240  0.897  1.0
  O  O24  1  0.859  0.060  0.340  1.0
  O  O25  1  0.060  0.859  0.840  1.0
  O  O26  1  0.180  0.503  0.289  1.0
  O  O27  1  0.503  0.180  0.789  1.0
  O  O28  1  0.993  0.719  0.121  1.0
  O  O29  1  0.719  0.993  0.621  1.0
  O  O30  1  0.439  0.808  0.457  1.0
  O  O31  1  0.808  0.439  0.957  1.0
  O  O32  1  0.662  0.258  0.328  1.0
  O  O33  1  0.258  0.662  0.828  1.0
  O  O34  1  0.706  0.816  0.056  1.0
  O  O35  1  0.816  0.706  0.556  1.0
  O  O36  1  0.744  0.240  0.240  1.0
  O  O37  1  0.240  0.744  0.740  1.0
[/CIF]
.