The compound described by Ca3Mn2O7 crystallizes in the monoclinic P2_1 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(5), one O(6), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(7), and two equivalent O(6) atoms. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), one O(6), one O(7), and two equivalent O(5) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form corner-sharing MnO5 trigonal bipyramids. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form corner-sharing MnO5 square pyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), one Ca(3), one Mn(1), and one Mn(2) atom. 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 to one Ca(2), one Ca(3), one Mn(1), and one Mn(2) atom to form a mixture of distorted corner and edge-sharing OCa2Mn2 tetrahedra. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Ca(2), one Ca(3), and one Mn(1) atom. In the fifth O site, O(5) is bonded to one Ca(1), one Ca(2), two equivalent Ca(3), and one Mn(2) atom to form distorted OCa4Mn square pyramids that share  a cornercorner with one O(7)Ca4Mn square pyramid, corners with two equivalent O(5)Ca4Mn square pyramids, corners with two equivalent O(3)Ca2Mn2 tetrahedra, corners with two equivalent O(6)Ca4Mn trigonal bipyramids, edges with two equivalent O(7)Ca4Mn square pyramids,  an edgeedge with one O(3)Ca2Mn2 tetrahedra, and edges with two equivalent O(6)Ca4Mn trigonal bipyramids. In the sixth O site, O(6) is bonded to one Ca(1), one Ca(3), two equivalent Ca(2), and one Mn(2) atom to form distorted OCa4Mn trigonal bipyramids that share  a cornercorner with one O(7)Ca4Mn square pyramid, corners with two equivalent O(5)Ca4Mn square pyramids, corners with two equivalent O(3)Ca2Mn2 tetrahedra, corners with two equivalent O(6)Ca4Mn trigonal bipyramids, edges with two equivalent O(5)Ca4Mn square pyramids, edges with two equivalent O(7)Ca4Mn square pyramids, and  an edgeedge with one O(3)Ca2Mn2 tetrahedra. In the seventh O site, O(7) is bonded to one Ca(2), one Ca(3), two equivalent Ca(1), and one Mn(1) atom to form distorted OCa4Mn square pyramids that share  a cornercorner with one O(5)Ca4Mn square pyramid, corners with two equivalent O(7)Ca4Mn square pyramids,  a cornercorner with one O(3)Ca2Mn2 tetrahedra,  a cornercorner with one O(6)Ca4Mn trigonal bipyramid, edges with two equivalent O(5)Ca4Mn square pyramids,  an edgeedge with one O(3)Ca2Mn2 tetrahedra, and edges with two equivalent O(6)Ca4Mn trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca3Mn2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.201
_cell_length_b   5.145
_cell_length_c   6.656
_cell_angle_alpha   67.573
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   322.911
_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  0.130  0.852  0.320  1.0
  Ca  Ca1  1  0.396  0.669  0.679  1.0
  Ca  Ca2  1  0.630  0.148  0.680  1.0
  Ca  Ca3  1  0.896  0.331  0.321  1.0
  Ca  Ca4  1  0.374  0.362  0.318  1.0
  Ca  Ca5  1  0.874  0.638  0.682  1.0
  Mn  Mn6  1  0.137  0.502  0.974  1.0
  Mn  Mn7  1  0.363  0.993  0.996  1.0
  Mn  Mn8  1  0.637  0.498  0.026  1.0
  Mn  Mn9  1  0.863  0.007  0.004  1.0
  O  O10  1  0.479  0.704  0.006  1.0
  O  O11  1  0.979  0.296  0.994  1.0
  O  O12  1  0.701  0.153  0.024  1.0
  O  O13  1  0.799  0.660  0.011  1.0
  O  O14  1  0.201  0.847  0.976  1.0
  O  O15  1  0.299  0.340  0.989  1.0
  O  O16  1  0.117  0.667  0.679  1.0
  O  O17  1  0.358  0.854  0.310  1.0
  O  O18  1  0.617  0.333  0.321  1.0
  O  O19  1  0.858  0.146  0.690  1.0
  O  O20  1  0.905  0.822  0.307  1.0
  O  O21  1  0.628  0.631  0.717  1.0
  O  O22  1  0.128  0.369  0.283  1.0
  O  O23  1  0.405  0.178  0.693  1.0
[/CIF]
.
The compound described by Ca3Mn2O7 crystallizes in the monoclinic P2_1 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(2), one O(4), one O(5), one O(6), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(7), and two equivalent O(6) atoms. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), one O(6), one O(7), and two equivalent O(5) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form corner-sharing MnO5 trigonal bipyramids. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form corner-sharing MnO5 square pyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), one Ca(3), one Mn(1), and one Mn(2) atom. 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 to one Ca(2), one Ca(3), one Mn(1), and one Mn(2) atom to form a mixture of distorted corner and edge-sharing OCa2Mn2 tetrahedra. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Ca(2), one Ca(3), and one Mn(1) atom. In the fifth O site, O(5) is bonded to one Ca(1), one Ca(2), two equivalent Ca(3), and one Mn(2) atom to form distorted OCa4Mn square pyramids that share  a cornercorner with one O(7)Ca4Mn square pyramid, corners with two equivalent O(5)Ca4Mn square pyramids, corners with two equivalent O(3)Ca2Mn2 tetrahedra, corners with two equivalent O(6)Ca4Mn trigonal bipyramids, edges with two equivalent O(7)Ca4Mn square pyramids,  an edgeedge with one O(3)Ca2Mn2 tetrahedra, and edges with two equivalent O(6)Ca4Mn trigonal bipyramids. In the sixth O site, O(6) is bonded to one Ca(1), one Ca(3), two equivalent Ca(2), and one Mn(2) atom to form distorted OCa4Mn trigonal bipyramids that share  a cornercorner with one O(7)Ca4Mn square pyramid, corners with two equivalent O(5)Ca4Mn square pyramids, corners with two equivalent O(3)Ca2Mn2 tetrahedra, corners with two equivalent O(6)Ca4Mn trigonal bipyramids, edges with two equivalent O(5)Ca4Mn square pyramids, edges with two equivalent O(7)Ca4Mn square pyramids, and  an edgeedge with one O(3)Ca2Mn2 tetrahedra. In the seventh O site, O(7) is bonded to one Ca(2), one Ca(3), two equivalent Ca(1), and one Mn(1) atom to form distorted OCa4Mn square pyramids that share  a cornercorner with one O(5)Ca4Mn square pyramid, corners with two equivalent O(7)Ca4Mn square pyramids,  a cornercorner with one O(3)Ca2Mn2 tetrahedra,  a cornercorner with one O(6)Ca4Mn trigonal bipyramid, edges with two equivalent O(5)Ca4Mn square pyramids,  an edgeedge with one O(3)Ca2Mn2 tetrahedra, and edges with two equivalent O(6)Ca4Mn trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca3Mn2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   10.201
_cell_length_b   5.145
_cell_length_c   6.656
_cell_angle_alpha   67.573
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   322.911
_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  0.130  0.852  0.320  1.0
  Ca  Ca1  1  0.396  0.669  0.679  1.0
  Ca  Ca2  1  0.630  0.148  0.680  1.0
  Ca  Ca3  1  0.896  0.331  0.321  1.0
  Ca  Ca4  1  0.374  0.362  0.318  1.0
  Ca  Ca5  1  0.874  0.638  0.682  1.0
  Mn  Mn6  1  0.137  0.502  0.974  1.0
  Mn  Mn7  1  0.363  0.993  0.996  1.0
  Mn  Mn8  1  0.637  0.498  0.026  1.0
  Mn  Mn9  1  0.863  0.007  0.004  1.0
  O  O10  1  0.479  0.704  0.006  1.0
  O  O11  1  0.979  0.296  0.994  1.0
  O  O12  1  0.701  0.153  0.024  1.0
  O  O13  1  0.799  0.660  0.011  1.0
  O  O14  1  0.201  0.847  0.976  1.0
  O  O15  1  0.299  0.340  0.989  1.0
  O  O16  1  0.117  0.667  0.679  1.0
  O  O17  1  0.358  0.854  0.310  1.0
  O  O18  1  0.617  0.333  0.321  1.0
  O  O19  1  0.858  0.146  0.690  1.0
  O  O20  1  0.905  0.822  0.307  1.0
  O  O21  1  0.628  0.631  0.717  1.0
  O  O22  1  0.128  0.369  0.283  1.0
  O  O23  1  0.405  0.178  0.693  1.0
[/CIF]
.