The material described by MgSi2O5 crystallizes in the orthorhombic Pbam space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted SiO5 square pyramids that share corners with four equivalent Si(2)O6 octahedra and  an edgeedge with one Si(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 49-51°. In the second Si site, Si(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form SiO6 octahedra that share corners with four equivalent Si(1)O5 square pyramids and edges with two equivalent Si(2)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Si(1) atoms to form a mixture of distorted edge and corner-sharing OMg2Si2 tetrahedra. In the third O site, O(3) is bonded to two equivalent Mg(1) and two equivalent Si(2) atoms to form a mixture of distorted edge and corner-sharing OMg2Si2 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Si(1) and two equivalent Si(2) atoms. is represented by the CIF file [CIF]
data_MgSi2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.357
_cell_length_b   6.944
_cell_length_c   7.735
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   287.721
_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  0.000  0.854  0.661  1.0
  Mg  Mg1  1  0.000  0.354  0.839  1.0
  Mg  Mg2  1  0.000  0.146  0.339  1.0
  Mg  Mg3  1  0.000  0.646  0.161  1.0
  Si  Si4  1  0.500  0.887  0.354  1.0
  Si  Si5  1  0.500  0.387  0.146  1.0
  Si  Si6  1  0.500  0.113  0.646  1.0
  Si  Si7  1  0.500  0.613  0.854  1.0
  Si  Si8  1  0.755  0.500  0.500  1.0
  Si  Si9  1  0.245  0.000  0.000  1.0
  Si  Si10  1  0.245  0.500  0.500  1.0
  Si  Si11  1  0.755  0.000  0.000  1.0
  O  O12  1  0.739  0.887  0.205  1.0
  O  O13  1  0.261  0.387  0.295  1.0
  O  O14  1  0.261  0.113  0.795  1.0
  O  O15  1  0.739  0.613  0.705  1.0
  O  O16  1  0.261  0.613  0.705  1.0
  O  O17  1  0.739  0.113  0.795  1.0
  O  O18  1  0.739  0.387  0.295  1.0
  O  O19  1  0.261  0.887  0.205  1.0
  O  O20  1  0.712  0.000  0.500  1.0
  O  O21  1  0.288  0.500  0.000  1.0
  O  O22  1  0.288  0.000  0.500  1.0
  O  O23  1  0.712  0.500  0.000  1.0
  O  O24  1  0.000  0.345  0.563  1.0
  O  O25  1  0.000  0.845  0.937  1.0
  O  O26  1  0.000  0.655  0.437  1.0
  O  O27  1  0.000  0.155  0.063  1.0
  O  O28  1  0.500  0.656  0.425  1.0
  O  O29  1  0.500  0.156  0.075  1.0
  O  O30  1  0.500  0.344  0.575  1.0
  O  O31  1  0.500  0.844  0.925  1.0
[/CIF]
.
The material described by MgSi2O5 crystallizes in the orthorhombic Pbam space group. Mg(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted SiO5 square pyramids that share corners with four equivalent Si(2)O6 octahedra and  an edgeedge with one Si(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 49-51°. In the second Si site, Si(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form SiO6 octahedra that share corners with four equivalent Si(1)O5 square pyramids and edges with two equivalent Si(2)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Si(1), and one Si(2) atom. In the second O site, O(2) is bonded to two equivalent Mg(1) and two equivalent Si(1) atoms to form a mixture of distorted edge and corner-sharing OMg2Si2 tetrahedra. In the third O site, O(3) is bonded to two equivalent Mg(1) and two equivalent Si(2) atoms to form a mixture of distorted edge and corner-sharing OMg2Si2 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Si(1) and two equivalent Si(2) atoms. is represented by the CIF file [CIF]
data_MgSi2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.357
_cell_length_b   6.944
_cell_length_c   7.735
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   287.721
_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  0.000  0.854  0.661  1.0
  Mg  Mg1  1  0.000  0.354  0.839  1.0
  Mg  Mg2  1  0.000  0.146  0.339  1.0
  Mg  Mg3  1  0.000  0.646  0.161  1.0
  Si  Si4  1  0.500  0.887  0.354  1.0
  Si  Si5  1  0.500  0.387  0.146  1.0
  Si  Si6  1  0.500  0.113  0.646  1.0
  Si  Si7  1  0.500  0.613  0.854  1.0
  Si  Si8  1  0.755  0.500  0.500  1.0
  Si  Si9  1  0.245  0.000  0.000  1.0
  Si  Si10  1  0.245  0.500  0.500  1.0
  Si  Si11  1  0.755  0.000  0.000  1.0
  O  O12  1  0.739  0.887  0.205  1.0
  O  O13  1  0.261  0.387  0.295  1.0
  O  O14  1  0.261  0.113  0.795  1.0
  O  O15  1  0.739  0.613  0.705  1.0
  O  O16  1  0.261  0.613  0.705  1.0
  O  O17  1  0.739  0.113  0.795  1.0
  O  O18  1  0.739  0.387  0.295  1.0
  O  O19  1  0.261  0.887  0.205  1.0
  O  O20  1  0.712  0.000  0.500  1.0
  O  O21  1  0.288  0.500  0.000  1.0
  O  O22  1  0.288  0.000  0.500  1.0
  O  O23  1  0.712  0.500  0.000  1.0
  O  O24  1  0.000  0.345  0.563  1.0
  O  O25  1  0.000  0.845  0.937  1.0
  O  O26  1  0.000  0.655  0.437  1.0
  O  O27  1  0.000  0.155  0.063  1.0
  O  O28  1  0.500  0.656  0.425  1.0
  O  O29  1  0.500  0.156  0.075  1.0
  O  O30  1  0.500  0.344  0.575  1.0
  O  O31  1  0.500  0.844  0.925  1.0
[/CIF]
.