The crystal structure described by CaMgSi2O6 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), one O(4), one O(5), two equivalent O(2), and two equivalent O(6) atoms. Mg(1) is bonded to one O(1), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with three equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(1)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, and  an edgeedge with one Si(1)O5 trigonal bipyramid. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), two equivalent O(2), and two equivalent O(3) atoms to form SiO5 trigonal bipyramids that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Si(1)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Si(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 34-55°. In the second Si site, Si(2) is bonded to one O(1), one O(5), and two equivalent O(6) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-62°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), two equivalent Mg(1), and one Si(2) atom. In the second O site, O(6) is bonded in a 2-coordinate geometry to two equivalent Ca(1) and two equivalent Si(2) atoms. In the third O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Mg(1), and one Si(2) atom. In the fourth O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Ca(1) and two equivalent Si(1) atoms. In the fifth O site, O(3) is bonded in a distorted see-saw-like geometry to one Ca(1), one Mg(1), and two equivalent Si(1) atoms. In the sixth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ca(1), two equivalent Mg(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaMg(SiO3)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.359
_cell_length_b   5.406
_cell_length_c   9.890
_cell_angle_alpha   89.321
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   446.863
_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
  Ca  Ca0  1  0.448  0.398  0.270  1.0
  Ca  Ca1  1  0.948  0.102  0.730  1.0
  Ca  Ca2  1  0.552  0.602  0.730  1.0
  Ca  Ca3  1  0.052  0.898  0.270  1.0
  Mg  Mg4  1  0.334  0.123  0.768  1.0
  Mg  Mg5  1  0.834  0.377  0.232  1.0
  Mg  Mg6  1  0.666  0.877  0.232  1.0
  Mg  Mg7  1  0.166  0.623  0.768  1.0
  Si  Si8  1  0.330  0.966  0.503  1.0
  Si  Si9  1  0.830  0.534  0.497  1.0
  Si  Si10  1  0.670  0.034  0.497  1.0
  Si  Si11  1  0.170  0.466  0.503  1.0
  Si  Si12  1  0.653  0.229  0.962  1.0
  Si  Si13  1  0.153  0.271  0.038  1.0
  Si  Si14  1  0.347  0.771  0.038  1.0
  Si  Si15  1  0.847  0.729  0.962  1.0
  O  O16  1  0.493  0.284  0.880  1.0
  O  O17  1  0.993  0.216  0.120  1.0
  O  O18  1  0.507  0.716  0.120  1.0
  O  O19  1  0.007  0.784  0.880  1.0
  O  O20  1  0.229  0.206  0.417  1.0
  O  O21  1  0.729  0.294  0.583  1.0
  O  O22  1  0.771  0.794  0.583  1.0
  O  O23  1  0.271  0.706  0.417  1.0
  O  O24  1  0.009  0.473  0.614  1.0
  O  O25  1  0.509  0.027  0.386  1.0
  O  O26  1  0.991  0.527  0.386  1.0
  O  O27  1  0.491  0.973  0.614  1.0
  O  O28  1  0.308  0.443  0.633  1.0
  O  O29  1  0.808  0.057  0.367  1.0
  O  O30  1  0.692  0.557  0.367  1.0
  O  O31  1  0.192  0.943  0.633  1.0
  O  O32  1  0.147  0.284  0.874  1.0
  O  O33  1  0.647  0.216  0.126  1.0
  O  O34  1  0.853  0.716  0.126  1.0
  O  O35  1  0.353  0.784  0.874  1.0
  O  O36  1  0.771  0.462  0.904  1.0
  O  O37  1  0.271  0.038  0.096  1.0
  O  O38  1  0.229  0.538  0.096  1.0
  O  O39  1  0.729  0.962  0.904  1.0
[/CIF]
.
The crystal structure described by CaMgSi2O6 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(3), one O(4), one O(5), two equivalent O(2), and two equivalent O(6) atoms. Mg(1) is bonded to one O(1), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with three equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(1)O5 trigonal bipyramids, edges with two equivalent Mg(1)O6 octahedra, and  an edgeedge with one Si(1)O5 trigonal bipyramid. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), two equivalent O(2), and two equivalent O(3) atoms to form SiO5 trigonal bipyramids that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Si(1)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Si(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 34-55°. In the second Si site, Si(2) is bonded to one O(1), one O(5), and two equivalent O(6) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-62°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), two equivalent Mg(1), and one Si(2) atom. In the second O site, O(6) is bonded in a 2-coordinate geometry to two equivalent Ca(1) and two equivalent Si(2) atoms. In the third O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Mg(1), and one Si(2) atom. In the fourth O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Ca(1) and two equivalent Si(1) atoms. In the fifth O site, O(3) is bonded in a distorted see-saw-like geometry to one Ca(1), one Mg(1), and two equivalent Si(1) atoms. In the sixth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Ca(1), two equivalent Mg(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaMg(SiO3)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.359
_cell_length_b   5.406
_cell_length_c   9.890
_cell_angle_alpha   89.321
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   446.863
_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
  Ca  Ca0  1  0.448  0.398  0.270  1.0
  Ca  Ca1  1  0.948  0.102  0.730  1.0
  Ca  Ca2  1  0.552  0.602  0.730  1.0
  Ca  Ca3  1  0.052  0.898  0.270  1.0
  Mg  Mg4  1  0.334  0.123  0.768  1.0
  Mg  Mg5  1  0.834  0.377  0.232  1.0
  Mg  Mg6  1  0.666  0.877  0.232  1.0
  Mg  Mg7  1  0.166  0.623  0.768  1.0
  Si  Si8  1  0.330  0.966  0.503  1.0
  Si  Si9  1  0.830  0.534  0.497  1.0
  Si  Si10  1  0.670  0.034  0.497  1.0
  Si  Si11  1  0.170  0.466  0.503  1.0
  Si  Si12  1  0.653  0.229  0.962  1.0
  Si  Si13  1  0.153  0.271  0.038  1.0
  Si  Si14  1  0.347  0.771  0.038  1.0
  Si  Si15  1  0.847  0.729  0.962  1.0
  O  O16  1  0.493  0.284  0.880  1.0
  O  O17  1  0.993  0.216  0.120  1.0
  O  O18  1  0.507  0.716  0.120  1.0
  O  O19  1  0.007  0.784  0.880  1.0
  O  O20  1  0.229  0.206  0.417  1.0
  O  O21  1  0.729  0.294  0.583  1.0
  O  O22  1  0.771  0.794  0.583  1.0
  O  O23  1  0.271  0.706  0.417  1.0
  O  O24  1  0.009  0.473  0.614  1.0
  O  O25  1  0.509  0.027  0.386  1.0
  O  O26  1  0.991  0.527  0.386  1.0
  O  O27  1  0.491  0.973  0.614  1.0
  O  O28  1  0.308  0.443  0.633  1.0
  O  O29  1  0.808  0.057  0.367  1.0
  O  O30  1  0.692  0.557  0.367  1.0
  O  O31  1  0.192  0.943  0.633  1.0
  O  O32  1  0.147  0.284  0.874  1.0
  O  O33  1  0.647  0.216  0.126  1.0
  O  O34  1  0.853  0.716  0.126  1.0
  O  O35  1  0.353  0.784  0.874  1.0
  O  O36  1  0.771  0.462  0.904  1.0
  O  O37  1  0.271  0.038  0.096  1.0
  O  O38  1  0.229  0.538  0.096  1.0
  O  O39  1  0.729  0.962  0.904  1.0
[/CIF]
.