The structure described by Mg2Fe5(SiO3)8 crystallizes in the monoclinic C2 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, and edges with two equivalent Fe(5)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(11), two equivalent O(3), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(11), two equivalent O(3), and two equivalent O(5) atoms. In the second Fe site, Fe(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(12) and two equivalent O(2) atoms. In the third Fe site, Fe(3) is bonded to two equivalent O(12), two equivalent O(2), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Fe(5)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to two equivalent O(11), two equivalent O(6), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra,  an edgeedge with one Fe(5)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. In the fifth Fe site, Fe(5) is bonded to two equivalent O(12), two equivalent O(6), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra,  an edgeedge with one Fe(4)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Fe(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-63°. In the second Si site, Si(2) is bonded to one O(1), one O(10), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one Fe(5)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-62°. In the third Si site, Si(3) is bonded to one O(11), one O(2), one O(4), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one Fe(4)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 37-61°. In the fourth Si site, Si(4) is bonded to one O(10), one O(12), one O(3), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one Fe(5)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-59°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Fe(2), one Fe(3), and one Si(3) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Mg(2), one Fe(1), and one Si(4) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Fe(1), one Si(2), and one Si(4) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(4), and one Fe(5) atom. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Fe(4), and one Si(1) atom. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Fe(3), one Fe(5), and one Si(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the eleventh O site, O(11) is bonded in a 4-coordinate geometry to one Mg(2), one Fe(1), one Fe(4), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), one Fe(3), one Fe(5), and one Si(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Fe5(SiO3)8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.362
_cell_length_b   10.362
_cell_length_c   5.379
_cell_angle_alpha   84.643
_cell_angle_beta   84.643
_cell_angle_gamma   124.310
_symmetry_Int_Tables_number   1
_cell_volume   467.458
_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  0.999  0.001  0.000  1.0
  Mg  Mg1  1  0.821  0.179  0.000  1.0
  Fe  Fe2  1  0.741  0.259  0.500  1.0
  Fe  Fe3  1  0.259  0.741  0.500  1.0
  Fe  Fe4  1  0.179  0.821  0.000  1.0
  Fe  Fe5  1  0.922  0.078  0.500  1.0
  Fe  Fe6  1  0.078  0.922  0.500  1.0
  Si  Si7  1  0.202  0.370  0.729  1.0
  Si  Si8  1  0.370  0.203  0.729  1.0
  Si  Si9  1  0.797  0.630  0.271  1.0
  Si  Si10  1  0.630  0.798  0.271  1.0
  Si  Si11  1  0.129  0.463  0.225  1.0
  Si  Si12  1  0.465  0.130  0.225  1.0
  Si  Si13  1  0.870  0.535  0.775  1.0
  Si  Si14  1  0.537  0.871  0.775  1.0
  O  O15  1  0.340  0.341  0.728  1.0
  O  O16  1  0.659  0.660  0.272  1.0
  O  O17  1  0.137  0.623  0.232  1.0
  O  O18  1  0.626  0.138  0.228  1.0
  O  O19  1  0.862  0.374  0.772  1.0
  O  O20  1  0.377  0.863  0.768  1.0
  O  O21  1  0.229  0.469  0.451  1.0
  O  O22  1  0.472  0.231  0.452  1.0
  O  O23  1  0.769  0.528  0.548  1.0
  O  O24  1  0.531  0.771  0.549  1.0
  O  O25  1  0.104  0.104  0.298  1.0
  O  O26  1  0.896  0.896  0.702  1.0
  O  O27  1  0.024  0.202  0.789  1.0
  O  O28  1  0.201  0.027  0.787  1.0
  O  O29  1  0.973  0.799  0.213  1.0
  O  O30  1  0.798  0.976  0.211  1.0
  O  O31  1  0.218  0.477  0.944  1.0
  O  O32  1  0.477  0.218  0.944  1.0
  O  O33  1  0.782  0.523  0.056  1.0
  O  O34  1  0.523  0.782  0.056  1.0
  O  O35  1  0.951  0.292  0.286  1.0
  O  O36  1  0.294  0.954  0.294  1.0
  O  O37  1  0.046  0.706  0.706  1.0
  O  O38  1  0.708  0.049  0.714  1.0
[/CIF]
.
The structure described by Mg2Fe5(SiO3)8 crystallizes in the monoclinic C2 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Fe(3)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, and edges with two equivalent Fe(5)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(11), two equivalent O(3), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(11), two equivalent O(3), and two equivalent O(5) atoms. In the second Fe site, Fe(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(12) and two equivalent O(2) atoms. In the third Fe site, Fe(3) is bonded to two equivalent O(12), two equivalent O(2), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Fe(5)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to two equivalent O(11), two equivalent O(6), and two equivalent O(7) atoms to form FeO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra,  an edgeedge with one Fe(5)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. In the fifth Fe site, Fe(5) is bonded to two equivalent O(12), two equivalent O(6), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra,  an edgeedge with one Fe(4)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Fe(4)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-63°. In the second Si site, Si(2) is bonded to one O(1), one O(10), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one Fe(5)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 58-62°. In the third Si site, Si(3) is bonded to one O(11), one O(2), one O(4), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one Fe(4)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 37-61°. In the fourth Si site, Si(4) is bonded to one O(10), one O(12), one O(3), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra,  a cornercorner with one Fe(5)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-59°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Fe(2), one Fe(3), and one Si(3) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Mg(2), one Fe(1), and one Si(4) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Fe(1), one Si(2), and one Si(4) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Fe(4), and one Fe(5) atom. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Fe(4), and one Si(1) atom. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Fe(3), one Fe(5), and one Si(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the eleventh O site, O(11) is bonded in a 4-coordinate geometry to one Mg(2), one Fe(1), one Fe(4), and one Si(3) atom. In the twelfth O site, O(12) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), one Fe(3), one Fe(5), and one Si(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Fe5(SiO3)8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.362
_cell_length_b   10.362
_cell_length_c   5.379
_cell_angle_alpha   84.643
_cell_angle_beta   84.643
_cell_angle_gamma   124.310
_symmetry_Int_Tables_number   1
_cell_volume   467.458
_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  0.999  0.001  0.000  1.0
  Mg  Mg1  1  0.821  0.179  0.000  1.0
  Fe  Fe2  1  0.741  0.259  0.500  1.0
  Fe  Fe3  1  0.259  0.741  0.500  1.0
  Fe  Fe4  1  0.179  0.821  0.000  1.0
  Fe  Fe5  1  0.922  0.078  0.500  1.0
  Fe  Fe6  1  0.078  0.922  0.500  1.0
  Si  Si7  1  0.202  0.370  0.729  1.0
  Si  Si8  1  0.370  0.203  0.729  1.0
  Si  Si9  1  0.797  0.630  0.271  1.0
  Si  Si10  1  0.630  0.798  0.271  1.0
  Si  Si11  1  0.129  0.463  0.225  1.0
  Si  Si12  1  0.465  0.130  0.225  1.0
  Si  Si13  1  0.870  0.535  0.775  1.0
  Si  Si14  1  0.537  0.871  0.775  1.0
  O  O15  1  0.340  0.341  0.728  1.0
  O  O16  1  0.659  0.660  0.272  1.0
  O  O17  1  0.137  0.623  0.232  1.0
  O  O18  1  0.626  0.138  0.228  1.0
  O  O19  1  0.862  0.374  0.772  1.0
  O  O20  1  0.377  0.863  0.768  1.0
  O  O21  1  0.229  0.469  0.451  1.0
  O  O22  1  0.472  0.231  0.452  1.0
  O  O23  1  0.769  0.528  0.548  1.0
  O  O24  1  0.531  0.771  0.549  1.0
  O  O25  1  0.104  0.104  0.298  1.0
  O  O26  1  0.896  0.896  0.702  1.0
  O  O27  1  0.024  0.202  0.789  1.0
  O  O28  1  0.201  0.027  0.787  1.0
  O  O29  1  0.973  0.799  0.213  1.0
  O  O30  1  0.798  0.976  0.211  1.0
  O  O31  1  0.218  0.477  0.944  1.0
  O  O32  1  0.477  0.218  0.944  1.0
  O  O33  1  0.782  0.523  0.056  1.0
  O  O34  1  0.523  0.782  0.056  1.0
  O  O35  1  0.951  0.292  0.286  1.0
  O  O36  1  0.294  0.954  0.294  1.0
  O  O37  1  0.046  0.706  0.706  1.0
  O  O38  1  0.708  0.049  0.714  1.0
[/CIF]
.