The material described by MgNiAs2O7 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded to one O(1), one O(5), one O(6), one O(7), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Ni(1)O5 trigonal bipyramids. Ni(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form NiO5 trigonal bipyramids that share corners with two equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form AsO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, and corners with two equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 53°. In the second As site, As(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, and corners with three equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 36-52°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a trigonal planar geometry to one Mg(1), one Ni(1), and one As(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one As(1) atom. In the third O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Ni(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Ni(1) and one As(1) atom. In the sixth O site, O(3) is bonded in a trigonal planar geometry to two equivalent Mg(1) and one As(1) atom. In the seventh O site, O(4) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. is represented by the CIF card [CIF]
data_MgNiAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.599
_cell_length_b   7.259
_cell_length_c   9.680
_cell_angle_alpha   66.625
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   554.576
_cell_formula_units_Z   4
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  0.074  0.731  0.894  1.0
  Mg  Mg1  1  0.574  0.269  0.606  1.0
  Mg  Mg2  1  0.926  0.269  0.106  1.0
  Mg  Mg3  1  0.426  0.731  0.394  1.0
  Ni  Ni4  1  0.939  0.183  0.685  1.0
  Ni  Ni5  1  0.439  0.817  0.815  1.0
  Ni  Ni6  1  0.061  0.817  0.315  1.0
  Ni  Ni7  1  0.561  0.183  0.185  1.0
  As  As8  1  0.772  0.563  0.752  1.0
  As  As9  1  0.272  0.437  0.748  1.0
  As  As10  1  0.228  0.437  0.248  1.0
  As  As11  1  0.728  0.563  0.252  1.0
  As  As12  1  0.720  0.976  0.960  1.0
  As  As13  1  0.220  0.024  0.540  1.0
  As  As14  1  0.280  0.024  0.040  1.0
  As  As15  1  0.780  0.976  0.460  1.0
  O  O16  1  0.731  0.133  0.053  1.0
  O  O17  1  0.231  0.867  0.447  1.0
  O  O18  1  0.269  0.867  0.947  1.0
  O  O19  1  0.769  0.133  0.553  1.0
  O  O20  1  0.595  0.645  0.772  1.0
  O  O21  1  0.095  0.355  0.728  1.0
  O  O22  1  0.405  0.355  0.228  1.0
  O  O23  1  0.905  0.645  0.272  1.0
  O  O24  1  0.902  0.532  0.893  1.0
  O  O25  1  0.402  0.468  0.607  1.0
  O  O26  1  0.098  0.468  0.107  1.0
  O  O27  1  0.598  0.532  0.393  1.0
  O  O28  1  0.857  0.740  0.582  1.0
  O  O29  1  0.357  0.260  0.918  1.0
  O  O30  1  0.143  0.260  0.418  1.0
  O  O31  1  0.643  0.740  0.082  1.0
  O  O32  1  0.923  0.031  0.327  1.0
  O  O33  1  0.423  0.969  0.173  1.0
  O  O34  1  0.077  0.969  0.673  1.0
  O  O35  1  0.577  0.031  0.827  1.0
  O  O36  1  0.738  0.356  0.208  1.0
  O  O37  1  0.238  0.644  0.292  1.0
  O  O38  1  0.262  0.644  0.792  1.0
  O  O39  1  0.762  0.356  0.708  1.0
  O  O40  1  0.603  0.949  0.391  1.0
  O  O41  1  0.103  0.051  0.109  1.0
  O  O42  1  0.397  0.051  0.609  1.0
  O  O43  1  0.897  0.949  0.891  1.0
[/CIF]
.
The material described by MgNiAs2O7 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded to one O(1), one O(5), one O(6), one O(7), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Ni(1)O5 trigonal bipyramids. Ni(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form NiO5 trigonal bipyramids that share corners with two equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form AsO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, and corners with two equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 53°. In the second As site, As(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, and corners with three equivalent Ni(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 36-52°. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a trigonal planar geometry to one Mg(1), one Ni(1), and one As(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one As(1) atom. In the third O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Ni(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ni(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Ni(1) and one As(1) atom. In the sixth O site, O(3) is bonded in a trigonal planar geometry to two equivalent Mg(1) and one As(1) atom. In the seventh O site, O(4) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. is represented by the CIF card [CIF]
data_MgNiAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.599
_cell_length_b   7.259
_cell_length_c   9.680
_cell_angle_alpha   66.625
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   554.576
_cell_formula_units_Z   4
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  0.074  0.731  0.894  1.0
  Mg  Mg1  1  0.574  0.269  0.606  1.0
  Mg  Mg2  1  0.926  0.269  0.106  1.0
  Mg  Mg3  1  0.426  0.731  0.394  1.0
  Ni  Ni4  1  0.939  0.183  0.685  1.0
  Ni  Ni5  1  0.439  0.817  0.815  1.0
  Ni  Ni6  1  0.061  0.817  0.315  1.0
  Ni  Ni7  1  0.561  0.183  0.185  1.0
  As  As8  1  0.772  0.563  0.752  1.0
  As  As9  1  0.272  0.437  0.748  1.0
  As  As10  1  0.228  0.437  0.248  1.0
  As  As11  1  0.728  0.563  0.252  1.0
  As  As12  1  0.720  0.976  0.960  1.0
  As  As13  1  0.220  0.024  0.540  1.0
  As  As14  1  0.280  0.024  0.040  1.0
  As  As15  1  0.780  0.976  0.460  1.0
  O  O16  1  0.731  0.133  0.053  1.0
  O  O17  1  0.231  0.867  0.447  1.0
  O  O18  1  0.269  0.867  0.947  1.0
  O  O19  1  0.769  0.133  0.553  1.0
  O  O20  1  0.595  0.645  0.772  1.0
  O  O21  1  0.095  0.355  0.728  1.0
  O  O22  1  0.405  0.355  0.228  1.0
  O  O23  1  0.905  0.645  0.272  1.0
  O  O24  1  0.902  0.532  0.893  1.0
  O  O25  1  0.402  0.468  0.607  1.0
  O  O26  1  0.098  0.468  0.107  1.0
  O  O27  1  0.598  0.532  0.393  1.0
  O  O28  1  0.857  0.740  0.582  1.0
  O  O29  1  0.357  0.260  0.918  1.0
  O  O30  1  0.143  0.260  0.418  1.0
  O  O31  1  0.643  0.740  0.082  1.0
  O  O32  1  0.923  0.031  0.327  1.0
  O  O33  1  0.423  0.969  0.173  1.0
  O  O34  1  0.077  0.969  0.673  1.0
  O  O35  1  0.577  0.031  0.827  1.0
  O  O36  1  0.738  0.356  0.208  1.0
  O  O37  1  0.238  0.644  0.292  1.0
  O  O38  1  0.262  0.644  0.792  1.0
  O  O39  1  0.762  0.356  0.708  1.0
  O  O40  1  0.603  0.949  0.391  1.0
  O  O41  1  0.103  0.051  0.109  1.0
  O  O42  1  0.397  0.051  0.609  1.0
  O  O43  1  0.897  0.949  0.891  1.0
[/CIF]
.