The material structure described by Mg5(Si2O7)4O2 crystallizes in the monoclinic C2/m space group. The structure consists of four water atoms inside a Mg5(Si2O7)4 framework. In the Mg5(Si2O7)4 framework, there are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form MgO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(3)O6 octahedra, and edges with four equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) 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, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Mg(3)O6 octahedra. In the third Mg site, Mg(3) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) 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(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(5), one O(7), and one O(8) 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 Mg(3)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-59°. In the second Si site, Si(2) is bonded to one O(3), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(3)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-55°. There are nine inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(2), one Mg(3), and one Si(2) atom. In the second O site, O(4) is bonded in a single-bond geometry to one Mg(3) and one O(10) atom. In the third O site, O(5) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the fourth O site, O(6) is bonded in a linear geometry to two equivalent Si(2) atoms. In the fifth O site, O(7) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(10) is bonded in a 2-coordinate geometry to two equivalent O(4) atoms. In the eighth O site, O(1) is bonded in a trigonal non-coplanar geometry to one Mg(1) and two equivalent Mg(2) atoms. In the ninth O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Mg(3), and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg5(Si4O15)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   11.484
_cell_length_b   11.484
_cell_length_c   5.346
_cell_angle_alpha   80.364
_cell_angle_beta   80.364
_cell_angle_gamma   105.720
_symmetry_Int_Tables_number   1
_cell_volume   652.004
_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  0.000  0.000  0.000  1.0
  Mg  Mg1  1  0.096  0.904  0.500  1.0
  Mg  Mg2  1  0.904  0.096  0.500  1.0
  Mg  Mg3  1  0.170  0.830  0.000  1.0
  Mg  Mg4  1  0.830  0.170  0.000  1.0
  Si  Si5  1  0.295  0.125  0.024  1.0
  Si  Si6  1  0.125  0.295  0.024  1.0
  Si  Si7  1  0.705  0.875  0.976  1.0
  Si  Si8  1  0.875  0.705  0.976  1.0
  Si  Si9  1  0.378  0.044  0.529  1.0
  Si  Si10  1  0.044  0.378  0.529  1.0
  Si  Si11  1  0.622  0.956  0.471  1.0
  Si  Si12  1  0.956  0.622  0.471  1.0
  O  O13  1  0.059  0.059  0.602  1.0
  O  O14  1  0.941  0.941  0.398  1.0
  O  O15  1  0.175  0.998  0.103  1.0
  O  O16  1  0.998  0.175  0.103  1.0
  O  O17  1  0.825  0.002  0.897  1.0
  O  O18  1  0.002  0.825  0.897  1.0
  O  O19  1  0.253  0.925  0.631  1.0
  O  O20  1  0.925  0.253  0.631  1.0
  O  O21  1  0.747  0.075  0.369  1.0
  O  O22  1  0.075  0.747  0.369  1.0
  O  O23  1  0.311  0.771  0.174  1.0
  O  O24  1  0.771  0.311  0.174  1.0
  O  O25  1  0.689  0.229  0.826  1.0
  O  O26  1  0.229  0.689  0.826  1.0
  O  O27  1  0.248  0.248  0.999  1.0
  O  O28  1  0.752  0.752  0.001  1.0
  O  O29  1  0.500  0.000  0.500  1.0
  O  O30  1  0.000  0.500  0.500  1.0
  O  O31  1  0.376  0.126  0.247  1.0
  O  O32  1  0.126  0.376  0.247  1.0
  O  O33  1  0.624  0.874  0.753  1.0
  O  O34  1  0.874  0.624  0.753  1.0
  O  O35  1  0.383  0.132  0.744  1.0
  O  O36  1  0.132  0.383  0.744  1.0
  O  O37  1  0.617  0.868  0.256  1.0
  O  O38  1  0.868  0.617  0.256  1.0
  O  O39  1  0.341  0.659  0.500  1.0
  O  O40  1  0.659  0.341  0.500  1.0
  O  O41  1  0.362  0.638  0.000  1.0
  O  O42  1  0.638  0.362  0.000  1.0
[/CIF]
.
The material structure described by Mg5(Si2O7)4O2 crystallizes in the monoclinic C2/m space group. The structure consists of four water atoms inside a Mg5(Si2O7)4 framework. In the Mg5(Si2O7)4 framework, there are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form MgO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(3)O6 octahedra, and edges with four equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) 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, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Mg(3)O6 octahedra. In the third Mg site, Mg(3) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) 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(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(5), one O(7), and one O(8) 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 Mg(3)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-59°. In the second Si site, Si(2) is bonded to one O(3), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(3)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-55°. There are nine inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(2), one Mg(3), and one Si(2) atom. In the second O site, O(4) is bonded in a single-bond geometry to one Mg(3) and one O(10) atom. In the third O site, O(5) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the fourth O site, O(6) is bonded in a linear geometry to two equivalent Si(2) atoms. In the fifth O site, O(7) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(10) is bonded in a 2-coordinate geometry to two equivalent O(4) atoms. In the eighth O site, O(1) is bonded in a trigonal non-coplanar geometry to one Mg(1) and two equivalent Mg(2) atoms. In the ninth O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Mg(3), and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg5(Si4O15)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   11.484
_cell_length_b   11.484
_cell_length_c   5.346
_cell_angle_alpha   80.364
_cell_angle_beta   80.364
_cell_angle_gamma   105.720
_symmetry_Int_Tables_number   1
_cell_volume   652.004
_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  0.000  0.000  0.000  1.0
  Mg  Mg1  1  0.096  0.904  0.500  1.0
  Mg  Mg2  1  0.904  0.096  0.500  1.0
  Mg  Mg3  1  0.170  0.830  0.000  1.0
  Mg  Mg4  1  0.830  0.170  0.000  1.0
  Si  Si5  1  0.295  0.125  0.024  1.0
  Si  Si6  1  0.125  0.295  0.024  1.0
  Si  Si7  1  0.705  0.875  0.976  1.0
  Si  Si8  1  0.875  0.705  0.976  1.0
  Si  Si9  1  0.378  0.044  0.529  1.0
  Si  Si10  1  0.044  0.378  0.529  1.0
  Si  Si11  1  0.622  0.956  0.471  1.0
  Si  Si12  1  0.956  0.622  0.471  1.0
  O  O13  1  0.059  0.059  0.602  1.0
  O  O14  1  0.941  0.941  0.398  1.0
  O  O15  1  0.175  0.998  0.103  1.0
  O  O16  1  0.998  0.175  0.103  1.0
  O  O17  1  0.825  0.002  0.897  1.0
  O  O18  1  0.002  0.825  0.897  1.0
  O  O19  1  0.253  0.925  0.631  1.0
  O  O20  1  0.925  0.253  0.631  1.0
  O  O21  1  0.747  0.075  0.369  1.0
  O  O22  1  0.075  0.747  0.369  1.0
  O  O23  1  0.311  0.771  0.174  1.0
  O  O24  1  0.771  0.311  0.174  1.0
  O  O25  1  0.689  0.229  0.826  1.0
  O  O26  1  0.229  0.689  0.826  1.0
  O  O27  1  0.248  0.248  0.999  1.0
  O  O28  1  0.752  0.752  0.001  1.0
  O  O29  1  0.500  0.000  0.500  1.0
  O  O30  1  0.000  0.500  0.500  1.0
  O  O31  1  0.376  0.126  0.247  1.0
  O  O32  1  0.126  0.376  0.247  1.0
  O  O33  1  0.624  0.874  0.753  1.0
  O  O34  1  0.874  0.624  0.753  1.0
  O  O35  1  0.383  0.132  0.744  1.0
  O  O36  1  0.132  0.383  0.744  1.0
  O  O37  1  0.617  0.868  0.256  1.0
  O  O38  1  0.868  0.617  0.256  1.0
  O  O39  1  0.341  0.659  0.500  1.0
  O  O40  1  0.659  0.341  0.500  1.0
  O  O41  1  0.362  0.638  0.000  1.0
  O  O42  1  0.638  0.362  0.000  1.0
[/CIF]
.