The crystal structure described by Ca3Mn2(Si2O7)2 is Esseneite-like structured and crystallizes in the monoclinic C2/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(2), one O(4), one O(6), two equivalent O(5), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MnO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mn(2)O6 octahedra. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mn(1)O6 octahedra. 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 Mn(1)O6 octahedra,  a cornercorner with one Mn(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-50°. 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 Mn(1)O6 octahedra,  a cornercorner with one Mn(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 66-67°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(2), one Mn(2), and one Si(2) atom to form distorted corner-sharing OCa2MnSi tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Mn(1), and one Mn(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(2), one Mn(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Mn(1), one Mn(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ca(1), one Si(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca3Mn2(Si2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.419
_cell_length_b   9.419
_cell_length_c   10.176
_cell_angle_alpha   60.009
_cell_angle_beta   60.009
_cell_angle_gamma   48.518
_symmetry_Int_Tables_number   1
_cell_volume   565.633
_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
  Ca  Ca0  1  0.231  0.161  0.542  1.0
  Ca  Ca1  1  0.839  0.769  0.958  1.0
  Ca  Ca2  1  0.161  0.231  0.042  1.0
  Ca  Ca3  1  0.654  0.346  0.250  1.0
  Ca  Ca4  1  0.769  0.839  0.458  1.0
  Ca  Ca5  1  0.346  0.654  0.750  1.0
  Mn  Mn6  1  0.214  0.786  0.250  1.0
  Mn  Mn7  1  0.786  0.214  0.750  1.0
  Mn  Mn8  1  0.000  0.000  0.000  1.0
  Mn  Mn9  1  0.000  0.000  0.500  1.0
  Si  Si10  1  0.111  0.534  0.659  1.0
  Si  Si11  1  0.534  0.111  0.159  1.0
  Si  Si12  1  0.214  0.533  0.146  1.0
  Si  Si13  1  0.533  0.214  0.646  1.0
  Si  Si14  1  0.466  0.889  0.841  1.0
  Si  Si15  1  0.786  0.467  0.854  1.0
  Si  Si16  1  0.467  0.786  0.354  1.0
  Si  Si17  1  0.889  0.466  0.341  1.0
  O  O18  1  0.296  0.876  0.504  1.0
  O  O19  1  0.895  0.972  0.719  1.0
  O  O20  1  0.649  0.457  0.810  1.0
  O  O21  1  0.972  0.895  0.219  1.0
  O  O22  1  0.943  0.264  0.482  1.0
  O  O23  1  0.508  0.050  0.815  1.0
  O  O24  1  0.457  0.649  0.310  1.0
  O  O25  1  0.736  0.057  0.018  1.0
  O  O26  1  0.492  0.950  0.185  1.0
  O  O27  1  0.675  0.657  0.406  1.0
  O  O28  1  0.105  0.028  0.281  1.0
  O  O29  1  0.057  0.736  0.518  1.0
  O  O30  1  0.950  0.492  0.685  1.0
  O  O31  1  0.876  0.296  0.004  1.0
  O  O32  1  0.657  0.675  0.906  1.0
  O  O33  1  0.264  0.943  0.982  1.0
  O  O34  1  0.471  0.894  0.678  1.0
  O  O35  1  0.325  0.343  0.594  1.0
  O  O36  1  0.106  0.529  0.822  1.0
  O  O37  1  0.343  0.325  0.094  1.0
  O  O38  1  0.050  0.508  0.315  1.0
  O  O39  1  0.028  0.105  0.781  1.0
  O  O40  1  0.894  0.471  0.178  1.0
  O  O41  1  0.351  0.543  0.190  1.0
  O  O42  1  0.529  0.106  0.322  1.0
  O  O43  1  0.543  0.351  0.690  1.0
  O  O44  1  0.124  0.704  0.996  1.0
  O  O45  1  0.704  0.124  0.496  1.0
[/CIF]
.
The crystal structure described by Ca3Mn2(Si2O7)2 is Esseneite-like structured and crystallizes in the monoclinic C2/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(2), one O(4), one O(6), two equivalent O(5), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MnO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mn(2)O6 octahedra. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mn(1)O6 octahedra. 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 Mn(1)O6 octahedra,  a cornercorner with one Mn(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 49-50°. 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 Mn(1)O6 octahedra,  a cornercorner with one Mn(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 66-67°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(2), one Mn(2), and one Si(2) atom to form distorted corner-sharing OCa2MnSi tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Mn(1), and one Mn(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(2), one Mn(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Mn(1), one Mn(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Ca(1), one Si(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca3Mn2(Si2O7)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.419
_cell_length_b   9.419
_cell_length_c   10.176
_cell_angle_alpha   60.009
_cell_angle_beta   60.009
_cell_angle_gamma   48.518
_symmetry_Int_Tables_number   1
_cell_volume   565.633
_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
  Ca  Ca0  1  0.231  0.161  0.542  1.0
  Ca  Ca1  1  0.839  0.769  0.958  1.0
  Ca  Ca2  1  0.161  0.231  0.042  1.0
  Ca  Ca3  1  0.654  0.346  0.250  1.0
  Ca  Ca4  1  0.769  0.839  0.458  1.0
  Ca  Ca5  1  0.346  0.654  0.750  1.0
  Mn  Mn6  1  0.214  0.786  0.250  1.0
  Mn  Mn7  1  0.786  0.214  0.750  1.0
  Mn  Mn8  1  0.000  0.000  0.000  1.0
  Mn  Mn9  1  0.000  0.000  0.500  1.0
  Si  Si10  1  0.111  0.534  0.659  1.0
  Si  Si11  1  0.534  0.111  0.159  1.0
  Si  Si12  1  0.214  0.533  0.146  1.0
  Si  Si13  1  0.533  0.214  0.646  1.0
  Si  Si14  1  0.466  0.889  0.841  1.0
  Si  Si15  1  0.786  0.467  0.854  1.0
  Si  Si16  1  0.467  0.786  0.354  1.0
  Si  Si17  1  0.889  0.466  0.341  1.0
  O  O18  1  0.296  0.876  0.504  1.0
  O  O19  1  0.895  0.972  0.719  1.0
  O  O20  1  0.649  0.457  0.810  1.0
  O  O21  1  0.972  0.895  0.219  1.0
  O  O22  1  0.943  0.264  0.482  1.0
  O  O23  1  0.508  0.050  0.815  1.0
  O  O24  1  0.457  0.649  0.310  1.0
  O  O25  1  0.736  0.057  0.018  1.0
  O  O26  1  0.492  0.950  0.185  1.0
  O  O27  1  0.675  0.657  0.406  1.0
  O  O28  1  0.105  0.028  0.281  1.0
  O  O29  1  0.057  0.736  0.518  1.0
  O  O30  1  0.950  0.492  0.685  1.0
  O  O31  1  0.876  0.296  0.004  1.0
  O  O32  1  0.657  0.675  0.906  1.0
  O  O33  1  0.264  0.943  0.982  1.0
  O  O34  1  0.471  0.894  0.678  1.0
  O  O35  1  0.325  0.343  0.594  1.0
  O  O36  1  0.106  0.529  0.822  1.0
  O  O37  1  0.343  0.325  0.094  1.0
  O  O38  1  0.050  0.508  0.315  1.0
  O  O39  1  0.028  0.105  0.781  1.0
  O  O40  1  0.894  0.471  0.178  1.0
  O  O41  1  0.351  0.543  0.190  1.0
  O  O42  1  0.529  0.106  0.322  1.0
  O  O43  1  0.543  0.351  0.690  1.0
  O  O44  1  0.124  0.704  0.996  1.0
  O  O45  1  0.704  0.124  0.496  1.0
[/CIF]
.