The compound described by MgFeAs2O7 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 pentagonal pyramids that share corners with six equivalent As(1)O4 tetrahedra and edges with three equivalent Fe(1)O6 pentagonal pyramids. Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted FeO6 pentagonal pyramids that share corners with six equivalent As(1)O4 tetrahedra and edges with three equivalent Mg(1)O6 pentagonal pyramids. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with three equivalent Mg(1)O6 pentagonal pyramids, corners with three equivalent Fe(1)O6 pentagonal pyramids, and  a cornercorner with one As(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one As(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent As(1) atoms. is represented by the CIF card [CIF]
data_MgFeAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.509
_cell_length_b   5.509
_cell_length_c   4.843
_cell_angle_alpha   82.646
_cell_angle_beta   97.325
_cell_angle_gamma   74.118
_symmetry_Int_Tables_number   1
_cell_volume   138.147
_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  0.761  0.761  0.000  1.0
  Fe  Fe1  1  0.138  0.139  1.000  1.0
  As  As2  1  0.689  0.217  0.400  1.0
  As  As3  1  0.217  0.689  0.600  1.0
  O  O4  1  0.846  0.045  0.725  1.0
  O  O5  1  0.855  0.376  0.204  1.0
  O  O6  1  0.523  0.055  0.212  1.0
  O  O7  1  0.045  0.846  0.275  1.0
  O  O8  1  0.375  0.855  0.796  1.0
  O  O9  1  0.056  0.523  0.788  1.0
  O  O10  1  0.483  0.483  0.500  1.0
[/CIF]
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The compound described by MgFeAs2O7 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 pentagonal pyramids that share corners with six equivalent As(1)O4 tetrahedra and edges with three equivalent Fe(1)O6 pentagonal pyramids. Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted FeO6 pentagonal pyramids that share corners with six equivalent As(1)O4 tetrahedra and edges with three equivalent Mg(1)O6 pentagonal pyramids. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with three equivalent Mg(1)O6 pentagonal pyramids, corners with three equivalent Fe(1)O6 pentagonal pyramids, and  a cornercorner with one As(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one As(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Fe(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent As(1) atoms. is represented by the CIF card [CIF]
data_MgFeAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.509
_cell_length_b   5.509
_cell_length_c   4.843
_cell_angle_alpha   82.646
_cell_angle_beta   97.325
_cell_angle_gamma   74.118
_symmetry_Int_Tables_number   1
_cell_volume   138.147
_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  0.761  0.761  0.000  1.0
  Fe  Fe1  1  0.138  0.139  1.000  1.0
  As  As2  1  0.689  0.217  0.400  1.0
  As  As3  1  0.217  0.689  0.600  1.0
  O  O4  1  0.846  0.045  0.725  1.0
  O  O5  1  0.855  0.376  0.204  1.0
  O  O6  1  0.523  0.055  0.212  1.0
  O  O7  1  0.045  0.846  0.275  1.0
  O  O8  1  0.375  0.855  0.796  1.0
  O  O9  1  0.056  0.523  0.788  1.0
  O  O10  1  0.483  0.483  0.500  1.0
[/CIF]
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