The compound described by Mg3Co2(Si2O7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(7) atoms to form MgO5 square pyramids that share  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Mg(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 41°. In the second Mg site, Mg(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Co(2)O6 octahedra, corners with two equivalent Mg(1)O5 square pyramids, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted CoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Mg(1)O5 square pyramids, and  an edgeedge with one Mg(2)O4 tetrahedra. In the second Co site, Co(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with two equivalent Mg(1)O5 square pyramids, corners with two equivalent Mg(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Co(1)O6 octahedra, and edges with two equivalent Mg(1)O5 square pyramids. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra, corners with three equivalent Mg(1)O5 square pyramids, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-62°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Mg(1)O5 square pyramid, corners with two equivalent Mg(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 64-73°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(2), one Co(2), and one Si(2) atom to form distorted corner-sharing OMg2CoSi tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Co(1), and one Co(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(2), one Co(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Co(1), one Co(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg3Co2(Si2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.293
_cell_length_b   9.293
_cell_length_c   9.742
_cell_angle_alpha   58.779
_cell_angle_beta   58.779
_cell_angle_gamma   47.845
_symmetry_Int_Tables_number   1
_cell_volume   513.693
_cell_formula_units_Z   2
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  0.085  0.256  0.107  1.0
  Mg  Mg1  1  0.744  0.915  0.393  1.0
  Mg  Mg2  1  0.256  0.085  0.607  1.0
  Mg  Mg3  1  0.386  0.614  0.750  1.0
  Mg  Mg4  1  0.915  0.744  0.893  1.0
  Mg  Mg5  1  0.614  0.386  0.250  1.0
  Co  Co6  1  0.788  0.212  0.750  1.0
  Co  Co7  1  0.212  0.788  0.250  1.0
  Co  Co8  1  0.000  0.000  0.000  1.0
  Co  Co9  1  0.000  0.000  0.500  1.0
  Si  Si10  1  0.542  0.089  0.707  1.0
  Si  Si11  1  0.089  0.542  0.207  1.0
  Si  Si12  1  0.525  0.238  0.104  1.0
  Si  Si13  1  0.238  0.525  0.604  1.0
  Si  Si14  1  0.911  0.458  0.793  1.0
  Si  Si15  1  0.475  0.762  0.896  1.0
  Si  Si16  1  0.762  0.475  0.396  1.0
  Si  Si17  1  0.458  0.911  0.293  1.0
  O  O18  1  0.839  0.303  0.322  1.0
  O  O19  1  0.973  0.891  0.415  1.0
  O  O20  1  0.453  0.636  0.091  1.0
  O  O21  1  0.891  0.973  0.915  1.0
  O  O22  1  0.235  0.988  0.301  1.0
  O  O23  1  0.061  0.514  0.618  1.0
  O  O24  1  0.636  0.453  0.591  1.0
  O  O25  1  0.012  0.765  0.199  1.0
  O  O26  1  0.939  0.486  0.382  1.0
  O  O27  1  0.630  0.683  0.265  1.0
  O  O28  1  0.027  0.109  0.585  1.0
  O  O29  1  0.765  0.012  0.699  1.0
  O  O30  1  0.486  0.939  0.882  1.0
  O  O31  1  0.303  0.839  0.822  1.0
  O  O32  1  0.683  0.630  0.765  1.0
  O  O33  1  0.988  0.235  0.801  1.0
  O  O34  1  0.913  0.481  0.945  1.0
  O  O35  1  0.370  0.317  0.735  1.0
  O  O36  1  0.519  0.087  0.555  1.0
  O  O37  1  0.317  0.370  0.235  1.0
  O  O38  1  0.514  0.061  0.118  1.0
  O  O39  1  0.109  0.027  0.085  1.0
  O  O40  1  0.481  0.913  0.445  1.0
  O  O41  1  0.547  0.364  0.909  1.0
  O  O42  1  0.087  0.519  0.055  1.0
  O  O43  1  0.364  0.547  0.409  1.0
  O  O44  1  0.697  0.161  0.178  1.0
  O  O45  1  0.161  0.697  0.678  1.0
[/CIF]
.
The compound described by Mg3Co2(Si2O7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(4), and two equivalent O(7) atoms to form MgO5 square pyramids that share  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Mg(2)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 41°. In the second Mg site, Mg(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Co(2)O6 octahedra, corners with two equivalent Mg(1)O5 square pyramids, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted CoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Co(2)O6 octahedra, edges with two equivalent Mg(1)O5 square pyramids, and  an edgeedge with one Mg(2)O4 tetrahedra. In the second Co site, Co(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form CoO6 octahedra that share corners with two equivalent Mg(1)O5 square pyramids, corners with two equivalent Mg(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Co(1)O6 octahedra, and edges with two equivalent Mg(1)O5 square pyramids. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra, corners with three equivalent Mg(1)O5 square pyramids, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-62°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Mg(1)O5 square pyramid, corners with two equivalent Mg(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 64-73°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(2), one Co(2), and one Si(2) atom to form distorted corner-sharing OMg2CoSi tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Co(1), and one Co(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(2), one Co(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Co(1), one Co(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Si(1) atom. is represented by the CIF file [CIF]
data_Mg3Co2(Si2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.293
_cell_length_b   9.293
_cell_length_c   9.742
_cell_angle_alpha   58.779
_cell_angle_beta   58.779
_cell_angle_gamma   47.845
_symmetry_Int_Tables_number   1
_cell_volume   513.693
_cell_formula_units_Z   2
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  0.085  0.256  0.107  1.0
  Mg  Mg1  1  0.744  0.915  0.393  1.0
  Mg  Mg2  1  0.256  0.085  0.607  1.0
  Mg  Mg3  1  0.386  0.614  0.750  1.0
  Mg  Mg4  1  0.915  0.744  0.893  1.0
  Mg  Mg5  1  0.614  0.386  0.250  1.0
  Co  Co6  1  0.788  0.212  0.750  1.0
  Co  Co7  1  0.212  0.788  0.250  1.0
  Co  Co8  1  0.000  0.000  0.000  1.0
  Co  Co9  1  0.000  0.000  0.500  1.0
  Si  Si10  1  0.542  0.089  0.707  1.0
  Si  Si11  1  0.089  0.542  0.207  1.0
  Si  Si12  1  0.525  0.238  0.104  1.0
  Si  Si13  1  0.238  0.525  0.604  1.0
  Si  Si14  1  0.911  0.458  0.793  1.0
  Si  Si15  1  0.475  0.762  0.896  1.0
  Si  Si16  1  0.762  0.475  0.396  1.0
  Si  Si17  1  0.458  0.911  0.293  1.0
  O  O18  1  0.839  0.303  0.322  1.0
  O  O19  1  0.973  0.891  0.415  1.0
  O  O20  1  0.453  0.636  0.091  1.0
  O  O21  1  0.891  0.973  0.915  1.0
  O  O22  1  0.235  0.988  0.301  1.0
  O  O23  1  0.061  0.514  0.618  1.0
  O  O24  1  0.636  0.453  0.591  1.0
  O  O25  1  0.012  0.765  0.199  1.0
  O  O26  1  0.939  0.486  0.382  1.0
  O  O27  1  0.630  0.683  0.265  1.0
  O  O28  1  0.027  0.109  0.585  1.0
  O  O29  1  0.765  0.012  0.699  1.0
  O  O30  1  0.486  0.939  0.882  1.0
  O  O31  1  0.303  0.839  0.822  1.0
  O  O32  1  0.683  0.630  0.765  1.0
  O  O33  1  0.988  0.235  0.801  1.0
  O  O34  1  0.913  0.481  0.945  1.0
  O  O35  1  0.370  0.317  0.735  1.0
  O  O36  1  0.519  0.087  0.555  1.0
  O  O37  1  0.317  0.370  0.235  1.0
  O  O38  1  0.514  0.061  0.118  1.0
  O  O39  1  0.109  0.027  0.085  1.0
  O  O40  1  0.481  0.913  0.445  1.0
  O  O41  1  0.547  0.364  0.909  1.0
  O  O42  1  0.087  0.519  0.055  1.0
  O  O43  1  0.364  0.547  0.409  1.0
  O  O44  1  0.697  0.161  0.178  1.0
  O  O45  1  0.161  0.697  0.678  1.0
[/CIF]
.