The crystal structure described by MgAl2As2(H7O8)2(H2O)2 crystallizes in the triclinic P-1 space group. The structure consists of two water molecules inside a MgAl2As2(H7O8)2 framework. In the MgAl2As2(H7O8)2 framework, Mg(1) is bonded to two equivalent O(5), two equivalent O(8), and two equivalent O(9) atoms to form MgO6 octahedra that share corners with two equivalent As(1)O4 tetrahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms to form AlO6 octahedra that share corners with two equivalent Al(2)O6 octahedra and corners with two equivalent As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. In the second Al site, Al(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form AlO6 octahedra that share corners with two equivalent Al(1)O6 octahedra and corners with four equivalent As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. As(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form AsO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, and corners with two equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-56°. There are seven inequivalent H sites. In the first H site, H(1) is bonded in a distorted single-bond geometry to one O(4) and one O(6) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(8) atom. In the third H site, H(3) is bonded in a distorted single-bond geometry to one O(6) atom. In the fourth H site, H(5) is bonded in a single-bond geometry to one O(9) atom. In the fifth H site, H(6) is bonded in a single-bond geometry to one O(9) atom. In the sixth H site, H(8) is bonded in a single-bond geometry to one O(2) and one O(8) atom. In the seventh H site, H(9) is bonded in a single-bond geometry to one O(1) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Al(1), one Al(2), and one H(9) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Al(2), one As(1), and one H(8) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Al(1) and one As(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Al(2), one As(1), and one H(1) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Mg(1) and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to one Al(1), one H(1), and one H(3) atom. In the seventh O site, O(8) is bonded in a 3-coordinate geometry to one Mg(1), one H(2), and one H(8) atom. In the eighth O site, O(9) is bonded in a distorted water-like geometry to one Mg(1), one H(5), and one H(6) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgAl2As2(HO)18
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.457
_cell_length_b   7.037
_cell_length_c   10.546
_cell_angle_alpha   97.840
_cell_angle_beta   101.704
_cell_angle_gamma   109.870
_symmetry_Int_Tables_number   1
_cell_volume   363.549
_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  0.500  0.000  0.500  1.0
  Al  Al1  1  0.000  0.500  0.000  1.0
  Al  Al2  1  0.000  0.000  0.000  1.0
  As  As3  1  0.483  0.074  0.834  1.0
  As  As4  1  0.517  0.926  0.166  1.0
  H  H5  1  0.905  0.311  0.170  1.0
  H  H6  1  0.095  0.689  0.830  1.0
  H  H7  1  0.022  0.005  0.622  1.0
  H  H8  1  0.978  0.995  0.378  1.0
  H  H9  1  0.835  0.506  0.220  1.0
  H  H10  1  0.165  0.494  0.780  1.0
  H  H11  1  0.559  0.589  0.762  1.0
  H  H12  1  0.441  0.411  0.238  1.0
  H  H13  1  0.689  0.400  0.453  1.0
  H  H14  1  0.311  0.600  0.547  1.0
  H  H15  1  0.805  0.408  0.605  1.0
  H  H16  1  0.195  0.592  0.395  1.0
  H  H17  1  0.410  0.352  0.686  1.0
  H  H18  1  0.590  0.648  0.314  1.0
  H  H19  1  0.805  0.945  0.705  1.0
  H  H20  1  0.195  0.055  0.295  1.0
  H  H21  1  0.682  0.671  0.008  1.0
  H  H22  1  0.318  0.329  0.992  1.0
  O  O23  1  0.871  0.716  0.005  1.0
  O  O24  1  0.129  0.284  0.995  1.0
  O  O25  1  0.694  0.938  0.847  1.0
  O  O26  1  0.306  0.062  0.153  1.0
  O  O27  1  0.628  0.317  0.936  1.0
  O  O28  1  0.372  0.683  0.064  1.0
  O  O29  1  0.194  0.936  0.876  1.0
  O  O30  1  0.806  0.064  0.124  1.0
  O  O31  1  0.389  0.093  0.672  1.0
  O  O32  1  0.611  0.907  0.328  1.0
  O  O33  1  0.973  0.468  0.183  1.0
  O  O34  1  0.027  0.532  0.817  1.0
  O  O35  1  0.394  0.491  0.696  1.0
  O  O36  1  0.606  0.509  0.304  1.0
  O  O37  1  0.826  0.959  0.614  1.0
  O  O38  1  0.174  0.041  0.386  1.0
  O  O39  1  0.735  0.317  0.516  1.0
  O  O40  1  0.265  0.683  0.484  1.0
[/CIF]
.
The crystal structure described by MgAl2As2(H7O8)2(H2O)2 crystallizes in the triclinic P-1 space group. The structure consists of two water molecules inside a MgAl2As2(H7O8)2 framework. In the MgAl2As2(H7O8)2 framework, Mg(1) is bonded to two equivalent O(5), two equivalent O(8), and two equivalent O(9) atoms to form MgO6 octahedra that share corners with two equivalent As(1)O4 tetrahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(6) atoms to form AlO6 octahedra that share corners with two equivalent Al(2)O6 octahedra and corners with two equivalent As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. In the second Al site, Al(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form AlO6 octahedra that share corners with two equivalent Al(1)O6 octahedra and corners with four equivalent As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. As(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form AsO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra, and corners with two equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-56°. There are seven inequivalent H sites. In the first H site, H(1) is bonded in a distorted single-bond geometry to one O(4) and one O(6) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(8) atom. In the third H site, H(3) is bonded in a distorted single-bond geometry to one O(6) atom. In the fourth H site, H(5) is bonded in a single-bond geometry to one O(9) atom. In the fifth H site, H(6) is bonded in a single-bond geometry to one O(9) atom. In the sixth H site, H(8) is bonded in a single-bond geometry to one O(2) and one O(8) atom. In the seventh H site, H(9) is bonded in a single-bond geometry to one O(1) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Al(1), one Al(2), and one H(9) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Al(2), one As(1), and one H(8) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Al(1) and one As(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Al(2), one As(1), and one H(1) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Mg(1) and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted water-like geometry to one Al(1), one H(1), and one H(3) atom. In the seventh O site, O(8) is bonded in a 3-coordinate geometry to one Mg(1), one H(2), and one H(8) atom. In the eighth O site, O(9) is bonded in a distorted water-like geometry to one Mg(1), one H(5), and one H(6) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgAl2As2(HO)18
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.457
_cell_length_b   7.037
_cell_length_c   10.546
_cell_angle_alpha   97.840
_cell_angle_beta   101.704
_cell_angle_gamma   109.870
_symmetry_Int_Tables_number   1
_cell_volume   363.549
_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  0.500  0.000  0.500  1.0
  Al  Al1  1  0.000  0.500  0.000  1.0
  Al  Al2  1  0.000  0.000  0.000  1.0
  As  As3  1  0.483  0.074  0.834  1.0
  As  As4  1  0.517  0.926  0.166  1.0
  H  H5  1  0.905  0.311  0.170  1.0
  H  H6  1  0.095  0.689  0.830  1.0
  H  H7  1  0.022  0.005  0.622  1.0
  H  H8  1  0.978  0.995  0.378  1.0
  H  H9  1  0.835  0.506  0.220  1.0
  H  H10  1  0.165  0.494  0.780  1.0
  H  H11  1  0.559  0.589  0.762  1.0
  H  H12  1  0.441  0.411  0.238  1.0
  H  H13  1  0.689  0.400  0.453  1.0
  H  H14  1  0.311  0.600  0.547  1.0
  H  H15  1  0.805  0.408  0.605  1.0
  H  H16  1  0.195  0.592  0.395  1.0
  H  H17  1  0.410  0.352  0.686  1.0
  H  H18  1  0.590  0.648  0.314  1.0
  H  H19  1  0.805  0.945  0.705  1.0
  H  H20  1  0.195  0.055  0.295  1.0
  H  H21  1  0.682  0.671  0.008  1.0
  H  H22  1  0.318  0.329  0.992  1.0
  O  O23  1  0.871  0.716  0.005  1.0
  O  O24  1  0.129  0.284  0.995  1.0
  O  O25  1  0.694  0.938  0.847  1.0
  O  O26  1  0.306  0.062  0.153  1.0
  O  O27  1  0.628  0.317  0.936  1.0
  O  O28  1  0.372  0.683  0.064  1.0
  O  O29  1  0.194  0.936  0.876  1.0
  O  O30  1  0.806  0.064  0.124  1.0
  O  O31  1  0.389  0.093  0.672  1.0
  O  O32  1  0.611  0.907  0.328  1.0
  O  O33  1  0.973  0.468  0.183  1.0
  O  O34  1  0.027  0.532  0.817  1.0
  O  O35  1  0.394  0.491  0.696  1.0
  O  O36  1  0.606  0.509  0.304  1.0
  O  O37  1  0.826  0.959  0.614  1.0
  O  O38  1  0.174  0.041  0.386  1.0
  O  O39  1  0.735  0.317  0.516  1.0
  O  O40  1  0.265  0.683  0.484  1.0
[/CIF]
.