The material described by CaAl4Si2O11 crystallizes in the monoclinic Cc space group. Ca(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), two equivalent O(7), two equivalent O(8), and two equivalent O(9) atoms to form CaO12 cuboctahedra that share corners with six equivalent Ca(1)O12 cuboctahedra, edges with two equivalent Al(4)O6 octahedra, edges with two equivalent Si(1)O6 octahedra, edges with two equivalent Si(2)O6 octahedra, edges with three equivalent Al(3)O4 trigonal pyramids, faces with three equivalent Al(1)O6 octahedra, and faces with three equivalent Al(2)O6 octahedra. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(2), one O(3), one O(7), one O(8), and one O(9) atom to form AlO6 octahedra that share corners with two equivalent Al(4)O6 octahedra, corners with two equivalent Si(1)O6 octahedra, corners with two equivalent Si(2)O6 octahedra, corners with three equivalent Al(3)O4 trigonal pyramids, faces with three equivalent Ca(1)O12 cuboctahedra, and  a faceface with one Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-56°. In the second Al site, Al(2) is bonded to one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form AlO6 octahedra that share corners with two equivalent Al(4)O6 octahedra, corners with two equivalent Si(1)O6 octahedra, corners with two equivalent Si(2)O6 octahedra, corners with three equivalent Al(3)O4 trigonal pyramids, faces with three equivalent Ca(1)O12 cuboctahedra, and  a faceface with one Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-56°. In the third Al site, Al(3) is bonded to one O(10), one O(7), one O(8), and one O(9) atom to form distorted AlO4 trigonal pyramids that share  a cornercorner with one Al(4)O6 octahedra,  a cornercorner with one Si(1)O6 octahedra,  a cornercorner with one Si(2)O6 octahedra, corners with three equivalent Al(1)O6 octahedra, corners with three equivalent Al(2)O6 octahedra, and edges with three equivalent Ca(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 32-60°. In the fourth Al site, Al(4) is bonded to one O(1), one O(10), one O(11), one O(2), one O(4), and one O(5) atom to form AlO6 octahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(3)O4 trigonal pyramid, edges with two equivalent Ca(1)O12 cuboctahedra, edges with two equivalent Si(1)O6 octahedra, and edges with two equivalent Si(2)O6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(10), one O(11), one O(3), one O(4), and one O(6) atom to form SiO6 octahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(3)O4 trigonal pyramid, edges with two equivalent Ca(1)O12 cuboctahedra, edges with two equivalent Al(4)O6 octahedra, and edges with two equivalent Si(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-54°. In the second Si site, Si(2) is bonded to one O(10), one O(11), one O(2), one O(3), one O(5), and one O(6) atom to form SiO6 octahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(3)O4 trigonal pyramid, edges with two equivalent Ca(1)O12 cuboctahedra, edges with two equivalent Al(4)O6 octahedra, and edges with two equivalent Si(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-54°. There are eleven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Al(2), one Al(4), and one Si(2) atom. In the second O site, O(6) is bonded in a 4-coordinate geometry to one Ca(1), one Al(2), one Si(1), and one Si(2) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Ca(1), one Al(1), one Al(2), and one Al(3) atom. In the fourth O site, O(8) is bonded in a 3-coordinate geometry to two equivalent Ca(1), one Al(1), one Al(2), and one Al(3) atom. In the fifth O site, O(9) is bonded in a 3-coordinate geometry to two equivalent Ca(1), one Al(1), one Al(2), and one Al(3) atom. In the sixth O site, O(10) is bonded in a rectangular see-saw-like geometry to one Al(3), one Al(4), one Si(1), and one Si(2) atom. In the seventh O site, O(11) is bonded in a 3-coordinate geometry to one Al(4), one Si(1), and one Si(2) atom. In the eighth O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), one Al(4), and one Si(1) atom. In the ninth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), one Al(4), and one Si(2) atom. In the tenth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), one Si(1), and one Si(2) atom. In the eleventh O site, O(4) is bonded in a 3-coordinate geometry to one Ca(1), one Al(2), one Al(4), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaAl4Si2O11
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.478
_cell_length_b   5.478
_cell_length_c   12.838
_cell_angle_alpha   89.817
_cell_angle_beta   89.817
_cell_angle_gamma   119.975
_symmetry_Int_Tables_number   1
_cell_volume   333.659
_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  0.666  0.333  0.753  1.0
  Ca  Ca1  1  0.333  0.666  0.253  1.0
  Al  Al2  1  0.003  0.008  0.646  1.0
  Al  Al3  1  0.996  0.991  0.352  1.0
  Al  Al4  1  0.008  0.003  0.146  1.0
  Al  Al5  1  0.991  0.996  0.852  1.0
  Al  Al6  1  0.332  0.665  0.729  1.0
  Al  Al7  1  0.665  0.332  0.229  1.0
  Al  Al8  1  0.501  0.003  0.499  1.0
  Al  Al9  1  0.003  0.501  0.999  1.0
  Si  Si10  1  0.995  0.498  0.498  1.0
  Si  Si11  1  0.503  0.498  0.498  1.0
  Si  Si12  1  0.498  0.995  0.998  1.0
  Si  Si13  1  0.498  0.503  0.998  1.0
  O  O14  1  0.190  0.837  0.078  1.0
  O  O15  1  0.189  0.352  0.078  1.0
  O  O16  1  0.648  0.824  0.077  1.0
  O  O17  1  0.810  0.164  0.922  1.0
  O  O18  1  0.811  0.648  0.922  1.0
  O  O19  1  0.354  0.177  0.924  1.0
  O  O20  1  0.837  0.190  0.578  1.0
  O  O21  1  0.824  0.648  0.577  1.0
  O  O22  1  0.352  0.189  0.578  1.0
  O  O23  1  0.164  0.810  0.422  1.0
  O  O24  1  0.177  0.354  0.424  1.0
  O  O25  1  0.648  0.811  0.422  1.0
  O  O26  1  0.151  0.848  0.749  1.0
  O  O27  1  0.150  0.303  0.753  1.0
  O  O28  1  0.696  0.849  0.745  1.0
  O  O29  1  0.848  0.151  0.249  1.0
  O  O30  1  0.849  0.696  0.245  1.0
  O  O31  1  0.303  0.150  0.253  1.0
  O  O32  1  0.328  0.656  0.578  1.0
  O  O33  1  0.674  0.347  0.425  1.0
  O  O34  1  0.656  0.328  0.078  1.0
  O  O35  1  0.347  0.674  0.925  1.0
[/CIF]
.
The material described by CaAl4Si2O11 crystallizes in the monoclinic Cc space group. Ca(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), two equivalent O(7), two equivalent O(8), and two equivalent O(9) atoms to form CaO12 cuboctahedra that share corners with six equivalent Ca(1)O12 cuboctahedra, edges with two equivalent Al(4)O6 octahedra, edges with two equivalent Si(1)O6 octahedra, edges with two equivalent Si(2)O6 octahedra, edges with three equivalent Al(3)O4 trigonal pyramids, faces with three equivalent Al(1)O6 octahedra, and faces with three equivalent Al(2)O6 octahedra. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(2), one O(3), one O(7), one O(8), and one O(9) atom to form AlO6 octahedra that share corners with two equivalent Al(4)O6 octahedra, corners with two equivalent Si(1)O6 octahedra, corners with two equivalent Si(2)O6 octahedra, corners with three equivalent Al(3)O4 trigonal pyramids, faces with three equivalent Ca(1)O12 cuboctahedra, and  a faceface with one Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-56°. In the second Al site, Al(2) is bonded to one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form AlO6 octahedra that share corners with two equivalent Al(4)O6 octahedra, corners with two equivalent Si(1)O6 octahedra, corners with two equivalent Si(2)O6 octahedra, corners with three equivalent Al(3)O4 trigonal pyramids, faces with three equivalent Ca(1)O12 cuboctahedra, and  a faceface with one Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-56°. In the third Al site, Al(3) is bonded to one O(10), one O(7), one O(8), and one O(9) atom to form distorted AlO4 trigonal pyramids that share  a cornercorner with one Al(4)O6 octahedra,  a cornercorner with one Si(1)O6 octahedra,  a cornercorner with one Si(2)O6 octahedra, corners with three equivalent Al(1)O6 octahedra, corners with three equivalent Al(2)O6 octahedra, and edges with three equivalent Ca(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 32-60°. In the fourth Al site, Al(4) is bonded to one O(1), one O(10), one O(11), one O(2), one O(4), and one O(5) atom to form AlO6 octahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(3)O4 trigonal pyramid, edges with two equivalent Ca(1)O12 cuboctahedra, edges with two equivalent Si(1)O6 octahedra, and edges with two equivalent Si(2)O6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(10), one O(11), one O(3), one O(4), and one O(6) atom to form SiO6 octahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(3)O4 trigonal pyramid, edges with two equivalent Ca(1)O12 cuboctahedra, edges with two equivalent Al(4)O6 octahedra, and edges with two equivalent Si(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-54°. In the second Si site, Si(2) is bonded to one O(10), one O(11), one O(2), one O(3), one O(5), and one O(6) atom to form SiO6 octahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra,  a cornercorner with one Al(3)O4 trigonal pyramid, edges with two equivalent Ca(1)O12 cuboctahedra, edges with two equivalent Al(4)O6 octahedra, and edges with two equivalent Si(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-54°. There are eleven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Al(2), one Al(4), and one Si(2) atom. In the second O site, O(6) is bonded in a 4-coordinate geometry to one Ca(1), one Al(2), one Si(1), and one Si(2) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Ca(1), one Al(1), one Al(2), and one Al(3) atom. In the fourth O site, O(8) is bonded in a 3-coordinate geometry to two equivalent Ca(1), one Al(1), one Al(2), and one Al(3) atom. In the fifth O site, O(9) is bonded in a 3-coordinate geometry to two equivalent Ca(1), one Al(1), one Al(2), and one Al(3) atom. In the sixth O site, O(10) is bonded in a rectangular see-saw-like geometry to one Al(3), one Al(4), one Si(1), and one Si(2) atom. In the seventh O site, O(11) is bonded in a 3-coordinate geometry to one Al(4), one Si(1), and one Si(2) atom. In the eighth O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), one Al(4), and one Si(1) atom. In the ninth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), one Al(4), and one Si(2) atom. In the tenth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), one Si(1), and one Si(2) atom. In the eleventh O site, O(4) is bonded in a 3-coordinate geometry to one Ca(1), one Al(2), one Al(4), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaAl4Si2O11
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.478
_cell_length_b   5.478
_cell_length_c   12.838
_cell_angle_alpha   89.817
_cell_angle_beta   89.817
_cell_angle_gamma   119.975
_symmetry_Int_Tables_number   1
_cell_volume   333.659
_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  0.666  0.333  0.753  1.0
  Ca  Ca1  1  0.333  0.666  0.253  1.0
  Al  Al2  1  0.003  0.008  0.646  1.0
  Al  Al3  1  0.996  0.991  0.352  1.0
  Al  Al4  1  0.008  0.003  0.146  1.0
  Al  Al5  1  0.991  0.996  0.852  1.0
  Al  Al6  1  0.332  0.665  0.729  1.0
  Al  Al7  1  0.665  0.332  0.229  1.0
  Al  Al8  1  0.501  0.003  0.499  1.0
  Al  Al9  1  0.003  0.501  0.999  1.0
  Si  Si10  1  0.995  0.498  0.498  1.0
  Si  Si11  1  0.503  0.498  0.498  1.0
  Si  Si12  1  0.498  0.995  0.998  1.0
  Si  Si13  1  0.498  0.503  0.998  1.0
  O  O14  1  0.190  0.837  0.078  1.0
  O  O15  1  0.189  0.352  0.078  1.0
  O  O16  1  0.648  0.824  0.077  1.0
  O  O17  1  0.810  0.164  0.922  1.0
  O  O18  1  0.811  0.648  0.922  1.0
  O  O19  1  0.354  0.177  0.924  1.0
  O  O20  1  0.837  0.190  0.578  1.0
  O  O21  1  0.824  0.648  0.577  1.0
  O  O22  1  0.352  0.189  0.578  1.0
  O  O23  1  0.164  0.810  0.422  1.0
  O  O24  1  0.177  0.354  0.424  1.0
  O  O25  1  0.648  0.811  0.422  1.0
  O  O26  1  0.151  0.848  0.749  1.0
  O  O27  1  0.150  0.303  0.753  1.0
  O  O28  1  0.696  0.849  0.745  1.0
  O  O29  1  0.848  0.151  0.249  1.0
  O  O30  1  0.849  0.696  0.245  1.0
  O  O31  1  0.303  0.150  0.253  1.0
  O  O32  1  0.328  0.656  0.578  1.0
  O  O33  1  0.674  0.347  0.425  1.0
  O  O34  1  0.656  0.328  0.078  1.0
  O  O35  1  0.347  0.674  0.925  1.0
[/CIF]
.