The structure described by CaSnAs2O7 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and two equivalent O(3) atoms to form distorted CaO7 pentagonal bipyramids that share  a cornercorner with one Sn(1)O5 square pyramid, corners with three equivalent As(2)O4 tetrahedra, corners with four equivalent As(1)O4 tetrahedra,  an edgeedge with one Ca(1)O7 pentagonal bipyramid, and edges with two equivalent Sn(1)O5 square pyramids. Sn(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form distorted SnO5 square pyramids that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid, corners with two equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with two equivalent Ca(1)O7 pentagonal bipyramids. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form AsO4 tetrahedra that share corners with four equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Sn(1)O5 square pyramids, and  a cornercorner with one As(2)O4 tetrahedra. In the second As site, As(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Ca(1)O7 pentagonal bipyramids, corners with three equivalent Sn(1)O5 square pyramids, and  a cornercorner with one As(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one As(2) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one As(1) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to one Ca(1), one Sn(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Sn(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one As(1) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one As(1) atom. In the seventh O site, O(4) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. is represented by the CIF card [CIF]
data_CaSnAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.473
_cell_length_b   7.911
_cell_length_c   9.973
_cell_angle_alpha   64.049
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   672.010
_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  0.054  0.736  0.923  1.0
  Ca  Ca1  1  0.554  0.264  0.577  1.0
  Ca  Ca2  1  0.946  0.264  0.077  1.0
  Ca  Ca3  1  0.446  0.736  0.423  1.0
  Sn  Sn4  1  0.952  0.239  0.644  1.0
  Sn  Sn5  1  0.452  0.761  0.856  1.0
  Sn  Sn6  1  0.048  0.761  0.356  1.0
  Sn  Sn7  1  0.548  0.239  0.144  1.0
  As  As8  1  0.756  0.585  0.725  1.0
  As  As9  1  0.256  0.415  0.775  1.0
  As  As10  1  0.244  0.415  0.275  1.0
  As  As11  1  0.744  0.585  0.225  1.0
  As  As12  1  0.724  0.996  0.941  1.0
  As  As13  1  0.224  0.004  0.559  1.0
  As  As14  1  0.276  0.004  0.059  1.0
  As  As15  1  0.776  0.996  0.441  1.0
  O  O16  1  0.741  0.125  0.038  1.0
  O  O17  1  0.241  0.875  0.462  1.0
  O  O18  1  0.259  0.875  0.962  1.0
  O  O19  1  0.759  0.125  0.538  1.0
  O  O20  1  0.587  0.669  0.706  1.0
  O  O21  1  0.087  0.331  0.794  1.0
  O  O22  1  0.413  0.331  0.294  1.0
  O  O23  1  0.913  0.669  0.206  1.0
  O  O24  1  0.859  0.564  0.872  1.0
  O  O25  1  0.359  0.436  0.628  1.0
  O  O26  1  0.141  0.436  0.128  1.0
  O  O27  1  0.641  0.564  0.372  1.0
  O  O28  1  0.838  0.765  0.562  1.0
  O  O29  1  0.338  0.235  0.938  1.0
  O  O30  1  0.162  0.235  0.438  1.0
  O  O31  1  0.662  0.765  0.062  1.0
  O  O32  1  0.913  0.045  0.320  1.0
  O  O33  1  0.413  0.955  0.180  1.0
  O  O34  1  0.087  0.955  0.680  1.0
  O  O35  1  0.587  0.045  0.820  1.0
  O  O36  1  0.744  0.386  0.196  1.0
  O  O37  1  0.244  0.614  0.304  1.0
  O  O38  1  0.256  0.614  0.804  1.0
  O  O39  1  0.756  0.386  0.696  1.0
  O  O40  1  0.615  0.990  0.362  1.0
  O  O41  1  0.115  0.010  0.138  1.0
  O  O42  1  0.385  0.010  0.638  1.0
  O  O43  1  0.885  0.990  0.862  1.0
[/CIF]
.
The structure described by CaSnAs2O7 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and two equivalent O(3) atoms to form distorted CaO7 pentagonal bipyramids that share  a cornercorner with one Sn(1)O5 square pyramid, corners with three equivalent As(2)O4 tetrahedra, corners with four equivalent As(1)O4 tetrahedra,  an edgeedge with one Ca(1)O7 pentagonal bipyramid, and edges with two equivalent Sn(1)O5 square pyramids. Sn(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form distorted SnO5 square pyramids that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid, corners with two equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with two equivalent Ca(1)O7 pentagonal bipyramids. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form AsO4 tetrahedra that share corners with four equivalent Ca(1)O7 pentagonal bipyramids, corners with two equivalent Sn(1)O5 square pyramids, and  a cornercorner with one As(2)O4 tetrahedra. In the second As site, As(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Ca(1)O7 pentagonal bipyramids, corners with three equivalent Sn(1)O5 square pyramids, and  a cornercorner with one As(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one As(2) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one As(1) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to one Ca(1), one Sn(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Sn(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Sn(1), and one As(1) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one As(1) atom. In the seventh O site, O(4) is bonded in a bent 120 degrees geometry to one As(1) and one As(2) atom. is represented by the CIF card [CIF]
data_CaSnAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.473
_cell_length_b   7.911
_cell_length_c   9.973
_cell_angle_alpha   64.049
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   672.010
_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  0.054  0.736  0.923  1.0
  Ca  Ca1  1  0.554  0.264  0.577  1.0
  Ca  Ca2  1  0.946  0.264  0.077  1.0
  Ca  Ca3  1  0.446  0.736  0.423  1.0
  Sn  Sn4  1  0.952  0.239  0.644  1.0
  Sn  Sn5  1  0.452  0.761  0.856  1.0
  Sn  Sn6  1  0.048  0.761  0.356  1.0
  Sn  Sn7  1  0.548  0.239  0.144  1.0
  As  As8  1  0.756  0.585  0.725  1.0
  As  As9  1  0.256  0.415  0.775  1.0
  As  As10  1  0.244  0.415  0.275  1.0
  As  As11  1  0.744  0.585  0.225  1.0
  As  As12  1  0.724  0.996  0.941  1.0
  As  As13  1  0.224  0.004  0.559  1.0
  As  As14  1  0.276  0.004  0.059  1.0
  As  As15  1  0.776  0.996  0.441  1.0
  O  O16  1  0.741  0.125  0.038  1.0
  O  O17  1  0.241  0.875  0.462  1.0
  O  O18  1  0.259  0.875  0.962  1.0
  O  O19  1  0.759  0.125  0.538  1.0
  O  O20  1  0.587  0.669  0.706  1.0
  O  O21  1  0.087  0.331  0.794  1.0
  O  O22  1  0.413  0.331  0.294  1.0
  O  O23  1  0.913  0.669  0.206  1.0
  O  O24  1  0.859  0.564  0.872  1.0
  O  O25  1  0.359  0.436  0.628  1.0
  O  O26  1  0.141  0.436  0.128  1.0
  O  O27  1  0.641  0.564  0.372  1.0
  O  O28  1  0.838  0.765  0.562  1.0
  O  O29  1  0.338  0.235  0.938  1.0
  O  O30  1  0.162  0.235  0.438  1.0
  O  O31  1  0.662  0.765  0.062  1.0
  O  O32  1  0.913  0.045  0.320  1.0
  O  O33  1  0.413  0.955  0.180  1.0
  O  O34  1  0.087  0.955  0.680  1.0
  O  O35  1  0.587  0.045  0.820  1.0
  O  O36  1  0.744  0.386  0.196  1.0
  O  O37  1  0.244  0.614  0.304  1.0
  O  O38  1  0.256  0.614  0.804  1.0
  O  O39  1  0.756  0.386  0.696  1.0
  O  O40  1  0.615  0.990  0.362  1.0
  O  O41  1  0.115  0.010  0.138  1.0
  O  O42  1  0.385  0.010  0.638  1.0
  O  O43  1  0.885  0.990  0.862  1.0
[/CIF]
.