The structure described by MgFeAs2O7 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one As(1)O4 tetrahedra, and edges with two equivalent Fe(1)O5 trigonal bipyramids. Fe(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form distorted FeO5 trigonal bipyramids that share corners with two equivalent As(2)O4 tetrahedra, corners with three equivalent As(1)O4 tetrahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one As(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with three equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second As site, As(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one As(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and corners with two equivalent Fe(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(1), and one As(1) atom. In the second O site, O(2) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one As(1) atom. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one As(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(1), and one As(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Mg(1) and one As(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgFeAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.822
_cell_length_b   5.674
_cell_length_c   5.361
_cell_angle_alpha   92.908
_cell_angle_beta   108.411
_cell_angle_gamma   77.712
_symmetry_Int_Tables_number   1
_cell_volume   164.170
_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  0.510  0.168  0.894  1.0
  Fe  Fe1  1  0.091  0.044  0.052  1.0
  As  As2  1  0.660  0.285  0.422  1.0
  As  As3  1  0.285  0.680  0.575  1.0
  O  O4  1  0.779  0.121  0.712  1.0
  O  O5  1  0.810  0.279  0.196  1.0
  O  O6  1  0.402  0.188  0.231  1.0
  O  O7  1  0.080  0.785  0.283  1.0
  O  O8  1  0.328  0.900  0.809  1.0
  O  O9  1  0.243  0.432  0.698  1.0
  O  O10  1  0.585  0.591  0.516  1.0
[/CIF]
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The structure described by MgFeAs2O7 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form distorted MgO5 trigonal bipyramids that share  a cornercorner with one As(1)O4 tetrahedra, corners with two equivalent As(2)O4 tetrahedra,  an edgeedge with one As(1)O4 tetrahedra, and edges with two equivalent Fe(1)O5 trigonal bipyramids. Fe(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form distorted FeO5 trigonal bipyramids that share corners with two equivalent As(2)O4 tetrahedra, corners with three equivalent As(1)O4 tetrahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one As(2)O4 tetrahedra,  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with three equivalent Fe(1)O5 trigonal bipyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second As site, As(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form AsO4 tetrahedra that share  a cornercorner with one As(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and corners with two equivalent Fe(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(1), and one As(1) atom. In the second O site, O(2) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one As(1) atom. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1), one Fe(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one As(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Fe(1), and one As(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Mg(1) and one As(2) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgFeAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.822
_cell_length_b   5.674
_cell_length_c   5.361
_cell_angle_alpha   92.908
_cell_angle_beta   108.411
_cell_angle_gamma   77.712
_symmetry_Int_Tables_number   1
_cell_volume   164.170
_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  0.510  0.168  0.894  1.0
  Fe  Fe1  1  0.091  0.044  0.052  1.0
  As  As2  1  0.660  0.285  0.422  1.0
  As  As3  1  0.285  0.680  0.575  1.0
  O  O4  1  0.779  0.121  0.712  1.0
  O  O5  1  0.810  0.279  0.196  1.0
  O  O6  1  0.402  0.188  0.231  1.0
  O  O7  1  0.080  0.785  0.283  1.0
  O  O8  1  0.328  0.900  0.809  1.0
  O  O9  1  0.243  0.432  0.698  1.0
  O  O10  1  0.585  0.591  0.516  1.0
[/CIF]
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