The material described by LiAlSi2H2O7 crystallizes in the triclinic P1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 5-coordinate geometry to one O(12), one O(2), one O(5), one O(7), and one O(9) atom. In the second Li site, Li(2) is bonded to one O(1), one O(12), one O(5), and one O(7) atom to form distorted LiO4 trigonal pyramids that share  a cornercorner with one Al(2)HO5 octahedra,  a cornercorner with one Si(2)HO3 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 54°. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 5-coordinate geometry to one O(1), one O(13), one O(3), one O(4), and one O(5) atom. In the second Al site, Al(2) is bonded to one H(1), one O(11), one O(14), one O(3), one O(6), and one O(7) atom to form distorted AlHO5 octahedra that share  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid,  an edgeedge with one Si(2)HO3 tetrahedra, and  an edgeedge with one Si(1)O5 trigonal bipyramid. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(10), one O(11), one O(6), and one O(9) atom to form SiO5 trigonal bipyramids that share  a cornercorner with one Si(2)HO3 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid, and  an edgeedge with one Al(2)HO5 octahedra. In the second Si site, Si(2) is bonded to one H(3), one O(14), one O(5), and one O(6) atom to form SiHO3 tetrahedra that share  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(1)O5 trigonal bipyramid,  a cornercorner with one Li(2)O4 trigonal pyramid, and  an edgeedge with one Al(2)HO5 octahedra. In the third Si site, Si(3) is bonded to one O(11), one O(12), one O(13), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)HO5 octahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(1)O5 trigonal bipyramid, and  a cornercorner with one Li(2)O4 trigonal pyramid. The corner-sharing octahedral tilt angles are 80°. In the fourth Si site, Si(4) is bonded to one O(14), one O(2), one O(4), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)HO5 octahedra,  a cornercorner with one Si(2)HO3 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one Al(2) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(9) atom. In the third H site, H(3) is bonded in a single-bond geometry to one Si(2) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(2) atom. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one Li(2), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Si(4), and one H(4) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Al(1), one Al(2), and one O(13) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(4) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Li(1), one Li(2), one Al(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Al(2), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Li(1), one Li(2), one Al(2), and one O(10) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Si(3) and one Si(4) atom. In the ninth O site, O(9) is bonded in a 1-coordinate geometry to one Li(1), one Si(1), and one H(2) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one Si(1) and one O(7) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal non-coplanar geometry to one Al(2), one Si(1), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one Li(1), one Li(2), and one Si(3) atom. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Al(1), one Si(3), and one O(3) atom. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Al(2), one Si(2), and one Si(4) atom. is represented by the CIF file [CIF]
data_LiAlSi2H2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.916
_cell_length_b   6.959
_cell_length_c   7.658
_cell_angle_alpha   62.497
_cell_angle_beta   89.714
_cell_angle_gamma   68.815
_symmetry_Int_Tables_number   1
_cell_volume   298.972
_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  0.163  0.988  0.616  1.0
  Li  Li1  1  0.572  0.899  0.640  1.0
  Al  Al2  1  0.958  0.576  0.753  1.0
  Al  Al3  1  0.452  0.016  0.018  1.0
  Si  Si4  1  0.524  0.470  0.877  1.0
  Si  Si5  1  0.823  0.989  0.883  1.0
  Si  Si6  1  0.291  0.298  0.227  1.0
  Si  Si7  1  0.948  0.598  0.325  1.0
  H  H8  1  0.407  0.865  0.231  1.0
  H  H9  1  0.293  0.623  0.586  1.0
  H  H10  1  0.999  0.052  0.903  1.0
  H  H11  1  0.753  0.400  0.324  1.0
  O  O12  1  0.717  0.533  0.778  1.0
  O  O13  1  0.879  0.371  0.406  1.0
  O  O14  1  0.167  0.265  0.904  1.0
  O  O15  1  0.967  0.663  0.496  1.0
  O  O16  1  0.862  0.864  0.745  1.0
  O  O17  1  0.585  0.211  0.822  1.0
  O  O18  1  0.423  0.893  0.856  1.0
  O  O19  1  0.171  0.540  0.242  1.0
  O  O20  1  0.291  0.635  0.708  1.0
  O  O21  1  0.465  0.641  0.998  1.0
  O  O22  1  0.490  0.263  0.104  1.0
  O  O23  1  0.343  0.077  0.440  1.0
  O  O24  1  0.090  0.360  0.046  1.0
  O  O25  1  0.778  0.821  0.112  1.0
[/CIF]
.
The material described by LiAlSi2H2O7 crystallizes in the triclinic P1 space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded in a 5-coordinate geometry to one O(12), one O(2), one O(5), one O(7), and one O(9) atom. In the second Li site, Li(2) is bonded to one O(1), one O(12), one O(5), and one O(7) atom to form distorted LiO4 trigonal pyramids that share  a cornercorner with one Al(2)HO5 octahedra,  a cornercorner with one Si(2)HO3 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 54°. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 5-coordinate geometry to one O(1), one O(13), one O(3), one O(4), and one O(5) atom. In the second Al site, Al(2) is bonded to one H(1), one O(11), one O(14), one O(3), one O(6), and one O(7) atom to form distorted AlHO5 octahedra that share  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid,  an edgeedge with one Si(2)HO3 tetrahedra, and  an edgeedge with one Si(1)O5 trigonal bipyramid. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(10), one O(11), one O(6), and one O(9) atom to form SiO5 trigonal bipyramids that share  a cornercorner with one Si(2)HO3 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Li(2)O4 trigonal pyramid, and  an edgeedge with one Al(2)HO5 octahedra. In the second Si site, Si(2) is bonded to one H(3), one O(14), one O(5), and one O(6) atom to form SiHO3 tetrahedra that share  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(1)O5 trigonal bipyramid,  a cornercorner with one Li(2)O4 trigonal pyramid, and  an edgeedge with one Al(2)HO5 octahedra. In the third Si site, Si(3) is bonded to one O(11), one O(12), one O(13), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)HO5 octahedra,  a cornercorner with one Si(4)O4 tetrahedra,  a cornercorner with one Si(1)O5 trigonal bipyramid, and  a cornercorner with one Li(2)O4 trigonal pyramid. The corner-sharing octahedral tilt angles are 80°. In the fourth Si site, Si(4) is bonded to one O(14), one O(2), one O(4), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(2)HO5 octahedra,  a cornercorner with one Si(2)HO3 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 43°. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one Al(2) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(9) atom. In the third H site, H(3) is bonded in a single-bond geometry to one Si(2) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(2) atom. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one Li(2), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Li(1), one Si(4), and one H(4) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Al(1), one Al(2), and one O(13) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(4) atom. In the fifth O site, O(5) is bonded in a 4-coordinate geometry to one Li(1), one Li(2), one Al(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Al(2), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Li(1), one Li(2), one Al(2), and one O(10) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Si(3) and one Si(4) atom. In the ninth O site, O(9) is bonded in a 1-coordinate geometry to one Li(1), one Si(1), and one H(2) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one Si(1) and one O(7) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal non-coplanar geometry to one Al(2), one Si(1), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one Li(1), one Li(2), and one Si(3) atom. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Al(1), one Si(3), and one O(3) atom. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Al(2), one Si(2), and one Si(4) atom. is represented by the CIF file [CIF]
data_LiAlSi2H2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.916
_cell_length_b   6.959
_cell_length_c   7.658
_cell_angle_alpha   62.497
_cell_angle_beta   89.714
_cell_angle_gamma   68.815
_symmetry_Int_Tables_number   1
_cell_volume   298.972
_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  0.163  0.988  0.616  1.0
  Li  Li1  1  0.572  0.899  0.640  1.0
  Al  Al2  1  0.958  0.576  0.753  1.0
  Al  Al3  1  0.452  0.016  0.018  1.0
  Si  Si4  1  0.524  0.470  0.877  1.0
  Si  Si5  1  0.823  0.989  0.883  1.0
  Si  Si6  1  0.291  0.298  0.227  1.0
  Si  Si7  1  0.948  0.598  0.325  1.0
  H  H8  1  0.407  0.865  0.231  1.0
  H  H9  1  0.293  0.623  0.586  1.0
  H  H10  1  0.999  0.052  0.903  1.0
  H  H11  1  0.753  0.400  0.324  1.0
  O  O12  1  0.717  0.533  0.778  1.0
  O  O13  1  0.879  0.371  0.406  1.0
  O  O14  1  0.167  0.265  0.904  1.0
  O  O15  1  0.967  0.663  0.496  1.0
  O  O16  1  0.862  0.864  0.745  1.0
  O  O17  1  0.585  0.211  0.822  1.0
  O  O18  1  0.423  0.893  0.856  1.0
  O  O19  1  0.171  0.540  0.242  1.0
  O  O20  1  0.291  0.635  0.708  1.0
  O  O21  1  0.465  0.641  0.998  1.0
  O  O22  1  0.490  0.263  0.104  1.0
  O  O23  1  0.343  0.077  0.440  1.0
  O  O24  1  0.090  0.360  0.046  1.0
  O  O25  1  0.778  0.821  0.112  1.0
[/CIF]
.