The material described by Ca2MgSi2O7 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ca sites. In the first Ca site, 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(6), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(5), one O(7), and two equivalent O(4) atoms. Mg(1) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form MgO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra and corners with two equivalent Mg(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Mg(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), one Mg(1), and one Si(2) atom. In the third O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(2), one Mg(1), and one Si(2) atom. In the fourth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one Si(2) atom. In the sixth O site, O(5) is bonded in a distorted tetrahedral geometry to one Ca(1), one Ca(2), one Mg(1), and one Si(1) atom. In the seventh O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Mg(1), and one Si(1) atom. is represented by the CIF file [CIF]
data_Ca2MgSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.814
_cell_length_b   9.223
_cell_length_c   9.975
_cell_angle_alpha   58.309
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   611.758
_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  0.556  0.081  0.199  1.0
  Ca  Ca1  1  0.718  0.569  0.974  1.0
  Ca  Ca2  1  0.782  0.569  0.474  1.0
  Ca  Ca3  1  0.056  0.919  0.301  1.0
  Ca  Ca4  1  0.444  0.919  0.801  1.0
  Ca  Ca5  1  0.944  0.081  0.699  1.0
  Ca  Ca6  1  0.218  0.431  0.526  1.0
  Ca  Ca7  1  0.282  0.431  0.026  1.0
  Mg  Mg8  1  0.897  0.284  0.887  1.0
  Mg  Mg9  1  0.603  0.284  0.387  1.0
  Mg  Mg10  1  0.103  0.716  0.113  1.0
  Mg  Mg11  1  0.397  0.716  0.613  1.0
  Si  Si12  1  0.271  0.113  0.417  1.0
  Si  Si13  1  0.960  0.340  0.288  1.0
  Si  Si14  1  0.729  0.887  0.583  1.0
  Si  Si15  1  0.460  0.660  0.212  1.0
  Si  Si16  1  0.771  0.887  0.083  1.0
  Si  Si17  1  0.040  0.660  0.712  1.0
  Si  Si18  1  0.229  0.113  0.917  1.0
  Si  Si19  1  0.540  0.340  0.788  1.0
  O  O20  1  0.727  0.322  0.725  1.0
  O  O21  1  0.562  0.504  0.360  1.0
  O  O22  1  0.071  0.160  0.341  1.0
  O  O23  1  0.429  0.160  0.841  1.0
  O  O24  1  0.571  0.840  0.159  1.0
  O  O25  1  0.048  0.643  0.556  1.0
  O  O26  1  0.062  0.496  0.140  1.0
  O  O27  1  0.094  0.248  0.782  1.0
  O  O28  1  0.452  0.643  0.056  1.0
  O  O29  1  0.313  0.931  0.433  1.0
  O  O30  1  0.594  0.752  0.718  1.0
  O  O31  1  0.548  0.357  0.944  1.0
  O  O32  1  0.906  0.752  0.218  1.0
  O  O33  1  0.773  0.322  0.225  1.0
  O  O34  1  0.938  0.504  0.860  1.0
  O  O35  1  0.278  0.126  0.573  1.0
  O  O36  1  0.952  0.357  0.444  1.0
  O  O37  1  0.778  0.874  0.927  1.0
  O  O38  1  0.273  0.678  0.275  1.0
  O  O39  1  0.929  0.840  0.659  1.0
  O  O40  1  0.222  0.126  0.073  1.0
  O  O41  1  0.687  0.069  0.567  1.0
  O  O42  1  0.227  0.678  0.775  1.0
  O  O43  1  0.438  0.496  0.640  1.0
  O  O44  1  0.813  0.069  0.067  1.0
  O  O45  1  0.187  0.931  0.933  1.0
  O  O46  1  0.722  0.874  0.427  1.0
  O  O47  1  0.406  0.248  0.282  1.0
[/CIF]
.
The material described by Ca2MgSi2O7 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ca sites. In the first Ca site, 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(6), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(5), one O(7), and two equivalent O(4) atoms. Mg(1) is bonded to one O(1), one O(2), one O(5), and one O(6) atom to form MgO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra and corners with two equivalent Mg(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Mg(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), one Mg(1), and one Si(2) atom. In the third O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(2), one Mg(1), and one Si(2) atom. In the fourth O site, O(3) is bonded in a 3-coordinate geometry to one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one Si(2) atom. In the sixth O site, O(5) is bonded in a distorted tetrahedral geometry to one Ca(1), one Ca(2), one Mg(1), and one Si(1) atom. In the seventh O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Mg(1), and one Si(1) atom. is represented by the CIF file [CIF]
data_Ca2MgSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.814
_cell_length_b   9.223
_cell_length_c   9.975
_cell_angle_alpha   58.309
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   611.758
_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  0.556  0.081  0.199  1.0
  Ca  Ca1  1  0.718  0.569  0.974  1.0
  Ca  Ca2  1  0.782  0.569  0.474  1.0
  Ca  Ca3  1  0.056  0.919  0.301  1.0
  Ca  Ca4  1  0.444  0.919  0.801  1.0
  Ca  Ca5  1  0.944  0.081  0.699  1.0
  Ca  Ca6  1  0.218  0.431  0.526  1.0
  Ca  Ca7  1  0.282  0.431  0.026  1.0
  Mg  Mg8  1  0.897  0.284  0.887  1.0
  Mg  Mg9  1  0.603  0.284  0.387  1.0
  Mg  Mg10  1  0.103  0.716  0.113  1.0
  Mg  Mg11  1  0.397  0.716  0.613  1.0
  Si  Si12  1  0.271  0.113  0.417  1.0
  Si  Si13  1  0.960  0.340  0.288  1.0
  Si  Si14  1  0.729  0.887  0.583  1.0
  Si  Si15  1  0.460  0.660  0.212  1.0
  Si  Si16  1  0.771  0.887  0.083  1.0
  Si  Si17  1  0.040  0.660  0.712  1.0
  Si  Si18  1  0.229  0.113  0.917  1.0
  Si  Si19  1  0.540  0.340  0.788  1.0
  O  O20  1  0.727  0.322  0.725  1.0
  O  O21  1  0.562  0.504  0.360  1.0
  O  O22  1  0.071  0.160  0.341  1.0
  O  O23  1  0.429  0.160  0.841  1.0
  O  O24  1  0.571  0.840  0.159  1.0
  O  O25  1  0.048  0.643  0.556  1.0
  O  O26  1  0.062  0.496  0.140  1.0
  O  O27  1  0.094  0.248  0.782  1.0
  O  O28  1  0.452  0.643  0.056  1.0
  O  O29  1  0.313  0.931  0.433  1.0
  O  O30  1  0.594  0.752  0.718  1.0
  O  O31  1  0.548  0.357  0.944  1.0
  O  O32  1  0.906  0.752  0.218  1.0
  O  O33  1  0.773  0.322  0.225  1.0
  O  O34  1  0.938  0.504  0.860  1.0
  O  O35  1  0.278  0.126  0.573  1.0
  O  O36  1  0.952  0.357  0.444  1.0
  O  O37  1  0.778  0.874  0.927  1.0
  O  O38  1  0.273  0.678  0.275  1.0
  O  O39  1  0.929  0.840  0.659  1.0
  O  O40  1  0.222  0.126  0.073  1.0
  O  O41  1  0.687  0.069  0.567  1.0
  O  O42  1  0.227  0.678  0.775  1.0
  O  O43  1  0.438  0.496  0.640  1.0
  O  O44  1  0.813  0.069  0.067  1.0
  O  O45  1  0.187  0.931  0.933  1.0
  O  O46  1  0.722  0.874  0.427  1.0
  O  O47  1  0.406  0.248  0.282  1.0
[/CIF]
.