The material described by LiAlSi2O7 crystallizes in the triclinic P1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form distorted LiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, corners with two equivalent Al(1)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. In the second Li site, Li(2) is bonded in a trigonal planar geometry to one O(13), one O(8), and one O(9) atom. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(13), 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(2)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra, and corners with two equivalent Si(4)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(10), one O(2), one O(8), and one O(9) atom to form AlO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. There are four inequivalent Si sites. In the first Si site, Si(1) 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(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra, and corners with two equivalent Al(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(11), one O(3), one O(4), and one O(5) 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 Si(3)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(10), one O(11), one O(12), and one O(4) 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(2)O4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(12), one O(13), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Li(1), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Li(1), one Al(2), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Li(1), one Al(1), and one Si(4) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Li(1) and one O(14) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Li(2), one Al(2), and one Si(4) atom. In the ninth O site, O(9) is bonded in a trigonal planar geometry to one Li(2), one Al(2), and one Si(1) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Al(2) 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(3) and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a trigonal planar geometry to one Li(2), one Al(1), and one Si(4) atom. In the fourteenth O site, O(14) is bonded in a single-bond geometry to one O(7) atom. is represented by the CIF card [CIF]
data_LiAlSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.066
_cell_length_b   7.687
_cell_length_c   8.770
_cell_angle_alpha   114.039
_cell_angle_beta   90.552
_cell_angle_gamma   89.902
_symmetry_Int_Tables_number   1
_cell_volume   311.844
_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
  Li  Li0  1  0.347  0.122  0.292  1.0
  Li  Li1  1  0.845  0.929  0.717  1.0
  Al  Al2  1  0.855  0.938  0.378  1.0
  Al  Al3  1  0.334  0.911  0.893  1.0
  Si  Si4  1  0.836  0.098  0.101  1.0
  Si  Si5  1  0.814  0.508  0.106  1.0
  Si  Si6  1  0.307  0.495  0.887  1.0
  Si  Si7  1  0.355  0.074  0.615  1.0
  O  O8  1  0.718  0.051  0.254  1.0
  O  O9  1  0.153  0.048  0.078  1.0
  O  O10  1  0.786  0.325  0.156  1.0
  O  O11  1  0.532  0.543  0.032  1.0
  O  O12  1  0.891  0.694  0.269  1.0
  O  O13  1  0.171  0.041  0.450  1.0
  O  O14  1  0.442  0.473  0.457  1.0
  O  O15  1  0.221  0.969  0.726  1.0
  O  O16  1  0.674  0.975  0.926  1.0
  O  O17  1  0.276  0.671  0.833  1.0
  O  O18  1  0.031  0.450  0.957  1.0
  O  O19  1  0.387  0.302  0.724  1.0
  O  O20  1  0.651  0.987  0.555  1.0
  O  O21  1  0.630  0.571  0.534  1.0
[/CIF]
.
The material described by LiAlSi2O7 crystallizes in the triclinic P1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form distorted LiO4 tetrahedra that share  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, corners with two equivalent Al(1)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. In the second Li site, Li(2) is bonded in a trigonal planar geometry to one O(13), one O(8), and one O(9) atom. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(13), 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(2)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra, and corners with two equivalent Si(4)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(10), one O(2), one O(8), and one O(9) atom to form AlO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. There are four inequivalent Si sites. In the first Si site, Si(1) 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(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Li(1)O4 tetrahedra, and corners with two equivalent Al(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(11), one O(3), one O(4), and one O(5) 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 Si(3)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(10), one O(11), one O(12), and one O(4) 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(2)O4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(12), one O(13), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Li(1)O4 tetrahedra,  a cornercorner with one Al(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one Li(1), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Li(1), one Al(2), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Li(1), one Al(1), and one Si(4) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Li(1) and one O(14) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Li(2), one Al(2), and one Si(4) atom. In the ninth O site, O(9) is bonded in a trigonal planar geometry to one Li(2), one Al(2), and one Si(1) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Al(2) 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(3) and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a trigonal planar geometry to one Li(2), one Al(1), and one Si(4) atom. In the fourteenth O site, O(14) is bonded in a single-bond geometry to one O(7) atom. is represented by the CIF card [CIF]
data_LiAlSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.066
_cell_length_b   7.687
_cell_length_c   8.770
_cell_angle_alpha   114.039
_cell_angle_beta   90.552
_cell_angle_gamma   89.902
_symmetry_Int_Tables_number   1
_cell_volume   311.844
_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
  Li  Li0  1  0.347  0.122  0.292  1.0
  Li  Li1  1  0.845  0.929  0.717  1.0
  Al  Al2  1  0.855  0.938  0.378  1.0
  Al  Al3  1  0.334  0.911  0.893  1.0
  Si  Si4  1  0.836  0.098  0.101  1.0
  Si  Si5  1  0.814  0.508  0.106  1.0
  Si  Si6  1  0.307  0.495  0.887  1.0
  Si  Si7  1  0.355  0.074  0.615  1.0
  O  O8  1  0.718  0.051  0.254  1.0
  O  O9  1  0.153  0.048  0.078  1.0
  O  O10  1  0.786  0.325  0.156  1.0
  O  O11  1  0.532  0.543  0.032  1.0
  O  O12  1  0.891  0.694  0.269  1.0
  O  O13  1  0.171  0.041  0.450  1.0
  O  O14  1  0.442  0.473  0.457  1.0
  O  O15  1  0.221  0.969  0.726  1.0
  O  O16  1  0.674  0.975  0.926  1.0
  O  O17  1  0.276  0.671  0.833  1.0
  O  O18  1  0.031  0.450  0.957  1.0
  O  O19  1  0.387  0.302  0.724  1.0
  O  O20  1  0.651  0.987  0.555  1.0
  O  O21  1  0.630  0.571  0.534  1.0
[/CIF]
.