The structure described by MgAl2(Si3O8)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a distorted pentagonal planar geometry to one O(1), one O(13), one O(14), one O(15), and one O(7) atom. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(14), one O(16), one O(2), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra, and corners with two equivalent Si(6)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(1), one O(13), one O(15), and one O(7) atom to form distorted AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(6)O4 tetrahedra, and corners with two equivalent Si(5)O4 tetrahedra. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(12), one O(4), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(11), one O(3), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(4)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(10), one O(11), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(12), one O(3), one O(5), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the fifth Si site, Si(5) is bonded to one O(13), one O(15), one O(2), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Al(2)O4 tetrahedra. In the sixth Si site, Si(6) is bonded to one O(1), one O(14), one O(16), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one Mg(1), one Al(2), and one Si(6) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(5) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Si(4) and one Si(6) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(5) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Mg(1), one Al(2), and one Si(1) atom. In the eighth O site, O(8) is bonded in a linear 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(2) and one Si(4) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a distorted T-shaped geometry to one Mg(1), one Al(2), and one Si(5) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal planar geometry to one Mg(1), one Al(1), and one Si(6) atom. In the fifteenth O site, O(15) is bonded in a distorted T-shaped geometry to one Mg(1), one Al(2), and one Si(5) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Al(1) and one Si(6) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgAl2(Si3O8)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.100
_cell_length_b   8.524
_cell_length_c   8.854
_cell_angle_alpha   94.678
_cell_angle_beta   91.144
_cell_angle_gamma   87.876
_symmetry_Int_Tables_number   1
_cell_volume   383.312
_cell_formula_units_Z   1
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
  Mg  Mg0  1  0.501  0.174  0.939  1.0
  Al  Al1  1  0.681  0.299  0.324  1.0
  Al  Al2  1  0.972  0.187  0.814  1.0
  Si  Si3  1  0.833  0.821  0.820  1.0
  Si  Si4  1  0.504  0.671  0.311  1.0
  Si  Si5  1  0.338  0.684  0.648  1.0
  Si  Si6  1  0.997  0.800  0.160  1.0
  Si  Si7  1  0.472  0.317  0.658  1.0
  Si  Si8  1  0.175  0.161  0.174  1.0
  O  O9  1  0.121  0.207  0.997  1.0
  O  O10  1  0.607  0.248  0.505  1.0
  O  O11  1  0.242  0.685  0.203  1.0
  O  O12  1  0.051  0.765  0.692  1.0
  O  O13  1  0.101  0.979  0.181  1.0
  O  O14  1  0.331  0.493  0.653  1.0
  O  O15  1  0.788  0.015  0.835  1.0
  O  O16  1  0.604  0.493  0.302  1.0
  O  O17  1  0.736  0.785  0.260  1.0
  O  O18  1  0.549  0.750  0.776  1.0
  O  O19  1  0.418  0.737  0.484  1.0
  O  O20  1  0.925  0.758  0.981  1.0
  O  O21  1  0.259  0.196  0.716  1.0
  O  O22  1  0.499  0.182  0.176  1.0
  O  O23  1  0.692  0.316  0.803  1.0
  O  O24  1  0.018  0.271  0.297  1.0
[/CIF]
.
The structure described by MgAl2(Si3O8)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a distorted pentagonal planar geometry to one O(1), one O(13), one O(14), one O(15), and one O(7) atom. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(14), one O(16), one O(2), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(5)O4 tetrahedra, and corners with two equivalent Si(6)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(1), one O(13), one O(15), and one O(7) atom to form distorted AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(6)O4 tetrahedra, and corners with two equivalent Si(5)O4 tetrahedra. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(12), one O(4), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(11), one O(3), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Si(4)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(10), one O(11), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(12), one O(3), one O(5), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the fifth Si site, Si(5) is bonded to one O(13), one O(15), one O(2), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Al(2)O4 tetrahedra. In the sixth Si site, Si(6) is bonded to one O(1), one O(14), one O(16), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one Mg(1), one Al(2), and one Si(6) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(5) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Si(4) and one Si(6) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(5) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Mg(1), one Al(2), and one Si(1) atom. In the eighth O site, O(8) is bonded in a linear 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(2) and one Si(4) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a distorted T-shaped geometry to one Mg(1), one Al(2), and one Si(5) atom. In the fourteenth O site, O(14) is bonded in a distorted trigonal planar geometry to one Mg(1), one Al(1), and one Si(6) atom. In the fifteenth O site, O(15) is bonded in a distorted T-shaped geometry to one Mg(1), one Al(2), and one Si(5) atom. In the sixteenth O site, O(16) is bonded in a bent 120 degrees geometry to one Al(1) and one Si(6) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgAl2(Si3O8)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.100
_cell_length_b   8.524
_cell_length_c   8.854
_cell_angle_alpha   94.678
_cell_angle_beta   91.144
_cell_angle_gamma   87.876
_symmetry_Int_Tables_number   1
_cell_volume   383.312
_cell_formula_units_Z   1
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
  Mg  Mg0  1  0.501  0.174  0.939  1.0
  Al  Al1  1  0.681  0.299  0.324  1.0
  Al  Al2  1  0.972  0.187  0.814  1.0
  Si  Si3  1  0.833  0.821  0.820  1.0
  Si  Si4  1  0.504  0.671  0.311  1.0
  Si  Si5  1  0.338  0.684  0.648  1.0
  Si  Si6  1  0.997  0.800  0.160  1.0
  Si  Si7  1  0.472  0.317  0.658  1.0
  Si  Si8  1  0.175  0.161  0.174  1.0
  O  O9  1  0.121  0.207  0.997  1.0
  O  O10  1  0.607  0.248  0.505  1.0
  O  O11  1  0.242  0.685  0.203  1.0
  O  O12  1  0.051  0.765  0.692  1.0
  O  O13  1  0.101  0.979  0.181  1.0
  O  O14  1  0.331  0.493  0.653  1.0
  O  O15  1  0.788  0.015  0.835  1.0
  O  O16  1  0.604  0.493  0.302  1.0
  O  O17  1  0.736  0.785  0.260  1.0
  O  O18  1  0.549  0.750  0.776  1.0
  O  O19  1  0.418  0.737  0.484  1.0
  O  O20  1  0.925  0.758  0.981  1.0
  O  O21  1  0.259  0.196  0.716  1.0
  O  O22  1  0.499  0.182  0.176  1.0
  O  O23  1  0.692  0.316  0.803  1.0
  O  O24  1  0.018  0.271  0.297  1.0
[/CIF]
.