The material described by Al2SiO5 crystallizes in the orthorhombic Cmcm space group. Al(1) is bonded in a 6-coordinate geometry to one O(3), two equivalent O(2), and three equivalent O(1) atoms. Si(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form corner-sharing SiO6 octahedra. The corner-sharing octahedral tilt angles are 32°. There are three inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Al(1) and one Si(1) atom to form distorted OAl3Si trigonal pyramids that share  a cornercorner with one O(3)Al2Si2 tetrahedra, corners with three equivalent O(1)Al3Si trigonal pyramids, edges with two equivalent O(3)Al2Si2 tetrahedra, and edges with two equivalent O(1)Al3Si trigonal pyramids. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Al(1) and one Si(1) atom. In the third O site, O(3) is bonded to two equivalent Al(1) and two equivalent Si(1) atoms to form distorted OAl2Si2 tetrahedra that share corners with two equivalent O(3)Al2Si2 tetrahedra, corners with two equivalent O(1)Al3Si trigonal pyramids, and edges with four equivalent O(1)Al3Si trigonal pyramids. is represented by the CIF card [CIF]
data_Al2SiO5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.974
_cell_length_b   4.974
_cell_length_c   9.171
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   137.978
_symmetry_Int_Tables_number   1
_cell_volume   151.864
_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
  Al  Al0  1  0.865  0.135  0.433  1.0
  Al  Al1  1  0.135  0.865  0.567  1.0
  Al  Al2  1  0.865  0.135  0.067  1.0
  Al  Al3  1  0.135  0.865  0.933  1.0
  Si  Si4  1  0.816  0.184  0.750  1.0
  Si  Si5  1  0.184  0.816  0.250  1.0
  O  O6  1  0.687  0.313  0.590  1.0
  O  O7  1  0.313  0.687  0.410  1.0
  O  O8  1  0.313  0.687  0.090  1.0
  O  O9  1  0.687  0.313  0.910  1.0
  O  O10  1  0.945  0.055  0.618  1.0
  O  O11  1  0.055  0.945  0.382  1.0
  O  O12  1  0.260  0.740  0.750  1.0
  O  O13  1  0.740  0.260  0.250  1.0
  O  O14  1  0.945  0.055  0.882  1.0
  O  O15  1  0.055  0.945  0.118  1.0
[/CIF]
.
The material described by Al2SiO5 crystallizes in the orthorhombic Cmcm space group. Al(1) is bonded in a 6-coordinate geometry to one O(3), two equivalent O(2), and three equivalent O(1) atoms. Si(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form corner-sharing SiO6 octahedra. The corner-sharing octahedral tilt angles are 32°. There are three inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Al(1) and one Si(1) atom to form distorted OAl3Si trigonal pyramids that share  a cornercorner with one O(3)Al2Si2 tetrahedra, corners with three equivalent O(1)Al3Si trigonal pyramids, edges with two equivalent O(3)Al2Si2 tetrahedra, and edges with two equivalent O(1)Al3Si trigonal pyramids. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Al(1) and one Si(1) atom. In the third O site, O(3) is bonded to two equivalent Al(1) and two equivalent Si(1) atoms to form distorted OAl2Si2 tetrahedra that share corners with two equivalent O(3)Al2Si2 tetrahedra, corners with two equivalent O(1)Al3Si trigonal pyramids, and edges with four equivalent O(1)Al3Si trigonal pyramids. is represented by the CIF card [CIF]
data_Al2SiO5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.974
_cell_length_b   4.974
_cell_length_c   9.171
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   137.978
_symmetry_Int_Tables_number   1
_cell_volume   151.864
_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
  Al  Al0  1  0.865  0.135  0.433  1.0
  Al  Al1  1  0.135  0.865  0.567  1.0
  Al  Al2  1  0.865  0.135  0.067  1.0
  Al  Al3  1  0.135  0.865  0.933  1.0
  Si  Si4  1  0.816  0.184  0.750  1.0
  Si  Si5  1  0.184  0.816  0.250  1.0
  O  O6  1  0.687  0.313  0.590  1.0
  O  O7  1  0.313  0.687  0.410  1.0
  O  O8  1  0.313  0.687  0.090  1.0
  O  O9  1  0.687  0.313  0.910  1.0
  O  O10  1  0.945  0.055  0.618  1.0
  O  O11  1  0.055  0.945  0.382  1.0
  O  O12  1  0.260  0.740  0.750  1.0
  O  O13  1  0.740  0.260  0.250  1.0
  O  O14  1  0.945  0.055  0.882  1.0
  O  O15  1  0.055  0.945  0.118  1.0
[/CIF]
.