The compound described by CaCrAs2O7 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(5), one O(6), two equivalent O(3), and two equivalent O(7) atoms. Cr(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form CrO5 square pyramids that share corners with two equivalent As(1)O4 tetrahedra and corners with three equivalent As(2)O4 tetrahedra. 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 two equivalent Cr(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 Cr(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 distorted trigonal planar geometry to one Ca(1), one Cr(1), and one As(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(1), one Cr(1), and one As(1) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Ca(1), one Cr(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Cr(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a 2-coordinate geometry to one Ca(1), one Cr(1), and one As(1) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar 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 file [CIF]
data_CaCrAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.192
_cell_length_b   7.506
_cell_length_c   9.580
_cell_angle_alpha   69.426
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   618.793
_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  0.065  0.749  0.933  1.0
  Ca  Ca1  1  0.565  0.251  0.567  1.0
  Ca  Ca2  1  0.935  0.251  0.067  1.0
  Ca  Ca3  1  0.435  0.749  0.433  1.0
  Cr  Cr4  1  0.950  0.216  0.676  1.0
  Cr  Cr5  1  0.450  0.784  0.824  1.0
  Cr  Cr6  1  0.050  0.784  0.324  1.0
  Cr  Cr7  1  0.550  0.216  0.176  1.0
  As  As8  1  0.764  0.579  0.735  1.0
  As  As9  1  0.264  0.421  0.765  1.0
  As  As10  1  0.236  0.421  0.265  1.0
  As  As11  1  0.736  0.579  0.235  1.0
  As  As12  1  0.706  0.977  0.957  1.0
  As  As13  1  0.206  0.023  0.543  1.0
  As  As14  1  0.294  0.023  0.043  1.0
  As  As15  1  0.794  0.977  0.457  1.0
  O  O16  1  0.691  0.145  0.038  1.0
  O  O17  1  0.191  0.855  0.462  1.0
  O  O18  1  0.309  0.855  0.962  1.0
  O  O19  1  0.809  0.145  0.538  1.0
  O  O20  1  0.587  0.652  0.721  1.0
  O  O21  1  0.087  0.348  0.779  1.0
  O  O22  1  0.413  0.348  0.279  1.0
  O  O23  1  0.913  0.652  0.221  1.0
  O  O24  1  0.863  0.566  0.889  1.0
  O  O25  1  0.363  0.434  0.611  1.0
  O  O26  1  0.137  0.434  0.111  1.0
  O  O27  1  0.637  0.566  0.389  1.0
  O  O28  1  0.860  0.752  0.582  1.0
  O  O29  1  0.360  0.248  0.918  1.0
  O  O30  1  0.140  0.248  0.418  1.0
  O  O31  1  0.640  0.752  0.082  1.0
  O  O32  1  0.909  0.003  0.311  1.0
  O  O33  1  0.409  0.997  0.189  1.0
  O  O34  1  0.091  0.997  0.689  1.0
  O  O35  1  0.591  0.003  0.811  1.0
  O  O36  1  0.729  0.373  0.197  1.0
  O  O37  1  0.229  0.627  0.303  1.0
  O  O38  1  0.271  0.627  0.803  1.0
  O  O39  1  0.771  0.373  0.697  1.0
  O  O40  1  0.616  0.982  0.412  1.0
  O  O41  1  0.116  0.018  0.088  1.0
  O  O42  1  0.384  0.018  0.588  1.0
  O  O43  1  0.884  0.982  0.912  1.0
[/CIF]
.
The compound described by CaCrAs2O7 crystallizes in the monoclinic P2_1/c space group. Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(5), one O(6), two equivalent O(3), and two equivalent O(7) atoms. Cr(1) is bonded to one O(1), one O(2), one O(5), one O(6), and one O(7) atom to form CrO5 square pyramids that share corners with two equivalent As(1)O4 tetrahedra and corners with three equivalent As(2)O4 tetrahedra. 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 two equivalent Cr(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 Cr(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 distorted trigonal planar geometry to one Ca(1), one Cr(1), and one As(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(1), one Cr(1), and one As(1) atom. In the third O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Ca(1), one Cr(1), and one As(2) atom. In the fourth O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Cr(1), and one As(2) atom. In the fifth O site, O(2) is bonded in a 2-coordinate geometry to one Ca(1), one Cr(1), and one As(1) atom. In the sixth O site, O(3) is bonded in a distorted trigonal planar 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 file [CIF]
data_CaCrAs2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.192
_cell_length_b   7.506
_cell_length_c   9.580
_cell_angle_alpha   69.426
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   618.793
_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  0.065  0.749  0.933  1.0
  Ca  Ca1  1  0.565  0.251  0.567  1.0
  Ca  Ca2  1  0.935  0.251  0.067  1.0
  Ca  Ca3  1  0.435  0.749  0.433  1.0
  Cr  Cr4  1  0.950  0.216  0.676  1.0
  Cr  Cr5  1  0.450  0.784  0.824  1.0
  Cr  Cr6  1  0.050  0.784  0.324  1.0
  Cr  Cr7  1  0.550  0.216  0.176  1.0
  As  As8  1  0.764  0.579  0.735  1.0
  As  As9  1  0.264  0.421  0.765  1.0
  As  As10  1  0.236  0.421  0.265  1.0
  As  As11  1  0.736  0.579  0.235  1.0
  As  As12  1  0.706  0.977  0.957  1.0
  As  As13  1  0.206  0.023  0.543  1.0
  As  As14  1  0.294  0.023  0.043  1.0
  As  As15  1  0.794  0.977  0.457  1.0
  O  O16  1  0.691  0.145  0.038  1.0
  O  O17  1  0.191  0.855  0.462  1.0
  O  O18  1  0.309  0.855  0.962  1.0
  O  O19  1  0.809  0.145  0.538  1.0
  O  O20  1  0.587  0.652  0.721  1.0
  O  O21  1  0.087  0.348  0.779  1.0
  O  O22  1  0.413  0.348  0.279  1.0
  O  O23  1  0.913  0.652  0.221  1.0
  O  O24  1  0.863  0.566  0.889  1.0
  O  O25  1  0.363  0.434  0.611  1.0
  O  O26  1  0.137  0.434  0.111  1.0
  O  O27  1  0.637  0.566  0.389  1.0
  O  O28  1  0.860  0.752  0.582  1.0
  O  O29  1  0.360  0.248  0.918  1.0
  O  O30  1  0.140  0.248  0.418  1.0
  O  O31  1  0.640  0.752  0.082  1.0
  O  O32  1  0.909  0.003  0.311  1.0
  O  O33  1  0.409  0.997  0.189  1.0
  O  O34  1  0.091  0.997  0.689  1.0
  O  O35  1  0.591  0.003  0.811  1.0
  O  O36  1  0.729  0.373  0.197  1.0
  O  O37  1  0.229  0.627  0.303  1.0
  O  O38  1  0.271  0.627  0.803  1.0
  O  O39  1  0.771  0.373  0.697  1.0
  O  O40  1  0.616  0.982  0.412  1.0
  O  O41  1  0.116  0.018  0.088  1.0
  O  O42  1  0.384  0.018  0.588  1.0
  O  O43  1  0.884  0.982  0.912  1.0
[/CIF]
.