The compound described by Co2As2O7 crystallizes in the triclinic P1 space group. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(12), one O(13), one O(4), one O(6), one O(8), and one O(9) atom to form distorted CoO6 octahedra that share  a cornercorner with one As(3)O4 tetrahedra, corners with two equivalent As(4)O4 tetrahedra,  a cornercorner with one As(1)O5 trigonal bipyramid,  a cornercorner with one As(2)O5 trigonal bipyramid,  an edgeedge with one Co(2)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and  an edgeedge with one As(2)O5 trigonal bipyramid. In the second Co site, Co(2) is bonded to one O(10), one O(11), one O(14), one O(4), one O(6), and one O(7) atom to form distorted CoO6 octahedra that share  a cornercorner with one As(3)O4 tetrahedra, corners with two equivalent As(4)O4 tetrahedra,  a cornercorner with one As(1)O5 trigonal bipyramid,  a cornercorner with one As(2)O5 trigonal bipyramid,  an edgeedge with one Co(1)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and  an edgeedge with one As(2)O5 trigonal bipyramid. In the third Co site, Co(3) is bonded to one O(10), one O(11), one O(14), one O(3), one O(5), and one O(7) atom to form distorted CoO6 octahedra that share  a cornercorner with one As(4)O4 tetrahedra, corners with two equivalent As(3)O4 tetrahedra,  a cornercorner with one As(1)O5 trigonal bipyramid,  a cornercorner with one As(2)O5 trigonal bipyramid,  an edgeedge with one Co(4)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, and  an edgeedge with one As(1)O5 trigonal bipyramid. In the fourth Co site, Co(4) is bonded to one O(12), one O(13), one O(3), one O(5), one O(8), and one O(9) atom to form distorted CoO6 octahedra that share  a cornercorner with one As(4)O4 tetrahedra, corners with two equivalent As(3)O4 tetrahedra,  a cornercorner with one As(1)O5 trigonal bipyramid,  a cornercorner with one As(2)O5 trigonal bipyramid,  an edgeedge with one Co(3)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, and  an edgeedge with one As(1)O5 trigonal bipyramid. There are four inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(5), one O(7), and one O(9) atom to form distorted AsO5 trigonal bipyramids that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Co(3)O6 octahedra,  a cornercorner with one Co(4)O6 octahedra, corners with two equivalent As(3)O4 tetrahedra,  an edgeedge with one Co(3)O6 octahedra, and  an edgeedge with one Co(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-52°. In the second As site, As(2) is bonded to one O(1), one O(10), one O(4), one O(6), and one O(8) atom to form distorted AsO5 trigonal bipyramids that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Co(3)O6 octahedra,  a cornercorner with one Co(4)O6 octahedra, corners with two equivalent As(4)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one Co(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-53°. In the third As site, As(3) is bonded to one O(11), one O(13), one O(2), and one O(5) atom to form AsO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra, corners with two equivalent Co(3)O6 octahedra, corners with two equivalent Co(4)O6 octahedra, and corners with two equivalent As(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 44-64°. In the fourth As site, As(4) is bonded to one O(1), one O(12), one O(14), and one O(6) atom to form AsO4 tetrahedra that share  a cornercorner with one Co(3)O6 octahedra,  a cornercorner with one Co(4)O6 octahedra, corners with two equivalent Co(1)O6 octahedra, corners with two equivalent Co(2)O6 octahedra, and corners with two equivalent As(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 44-64°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one As(2) and one As(4) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one As(1) and one As(3) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Co(3), one Co(4), and one As(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Co(3), one Co(4), one As(1), and one As(3) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Co(1), one Co(2), one As(2), and one As(4) atom. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Co(2), one Co(3), and one As(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Co(1), one Co(4), and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal non-coplanar geometry to one Co(1), one Co(4), and one As(1) atom. In the tenth O site, O(10) is bonded in a distorted trigonal non-coplanar geometry to one Co(2), one Co(3), and one As(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Co(2), one Co(3), and one As(3) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(4), and one As(4) atom. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Co(1), one Co(4), and one As(3) atom. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Co(2), one Co(3), and one As(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Co2As2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.812
_cell_length_b   5.326
_cell_length_c   5.366
_cell_angle_alpha   106.541
_cell_angle_beta   96.891
_cell_angle_gamma   97.161
_symmetry_Int_Tables_number   1
_cell_volume   129.042
_cell_formula_units_Z   1
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
  As  As0  1  0.100  0.746  0.743  1.0
  As  As1  1  0.902  0.220  0.222  1.0
  Co  Co2  1  0.494  0.687  0.311  1.0
  Co  Co3  1  0.491  0.312  0.701  1.0
  O  O4  1  0.082  0.030  0.007  1.0
  O  O5  1  0.750  0.620  0.626  1.0
  O  O6  1  0.197  0.423  0.426  1.0
  O  O7  1  0.282  0.926  0.580  1.0
  O  O8  1  0.283  0.589  0.927  1.0
  O  O9  1  0.705  0.391  0.069  1.0
  O  O10  1  0.713  0.056  0.387  1.0
[/CIF]
.
The compound described by Co2As2O7 crystallizes in the triclinic P1 space group. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(12), one O(13), one O(4), one O(6), one O(8), and one O(9) atom to form distorted CoO6 octahedra that share  a cornercorner with one As(3)O4 tetrahedra, corners with two equivalent As(4)O4 tetrahedra,  a cornercorner with one As(1)O5 trigonal bipyramid,  a cornercorner with one As(2)O5 trigonal bipyramid,  an edgeedge with one Co(2)O6 octahedra, edges with two equivalent Co(4)O6 octahedra, and  an edgeedge with one As(2)O5 trigonal bipyramid. In the second Co site, Co(2) is bonded to one O(10), one O(11), one O(14), one O(4), one O(6), and one O(7) atom to form distorted CoO6 octahedra that share  a cornercorner with one As(3)O4 tetrahedra, corners with two equivalent As(4)O4 tetrahedra,  a cornercorner with one As(1)O5 trigonal bipyramid,  a cornercorner with one As(2)O5 trigonal bipyramid,  an edgeedge with one Co(1)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and  an edgeedge with one As(2)O5 trigonal bipyramid. In the third Co site, Co(3) is bonded to one O(10), one O(11), one O(14), one O(3), one O(5), and one O(7) atom to form distorted CoO6 octahedra that share  a cornercorner with one As(4)O4 tetrahedra, corners with two equivalent As(3)O4 tetrahedra,  a cornercorner with one As(1)O5 trigonal bipyramid,  a cornercorner with one As(2)O5 trigonal bipyramid,  an edgeedge with one Co(4)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, and  an edgeedge with one As(1)O5 trigonal bipyramid. In the fourth Co site, Co(4) is bonded to one O(12), one O(13), one O(3), one O(5), one O(8), and one O(9) atom to form distorted CoO6 octahedra that share  a cornercorner with one As(4)O4 tetrahedra, corners with two equivalent As(3)O4 tetrahedra,  a cornercorner with one As(1)O5 trigonal bipyramid,  a cornercorner with one As(2)O5 trigonal bipyramid,  an edgeedge with one Co(3)O6 octahedra, edges with two equivalent Co(1)O6 octahedra, and  an edgeedge with one As(1)O5 trigonal bipyramid. There are four inequivalent As sites. In the first As site, As(1) is bonded to one O(2), one O(3), one O(5), one O(7), and one O(9) atom to form distorted AsO5 trigonal bipyramids that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Co(3)O6 octahedra,  a cornercorner with one Co(4)O6 octahedra, corners with two equivalent As(3)O4 tetrahedra,  an edgeedge with one Co(3)O6 octahedra, and  an edgeedge with one Co(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-52°. In the second As site, As(2) is bonded to one O(1), one O(10), one O(4), one O(6), and one O(8) atom to form distorted AsO5 trigonal bipyramids that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Co(3)O6 octahedra,  a cornercorner with one Co(4)O6 octahedra, corners with two equivalent As(4)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one Co(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-53°. In the third As site, As(3) is bonded to one O(11), one O(13), one O(2), and one O(5) atom to form AsO4 tetrahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra, corners with two equivalent Co(3)O6 octahedra, corners with two equivalent Co(4)O6 octahedra, and corners with two equivalent As(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 44-64°. In the fourth As site, As(4) is bonded to one O(1), one O(12), one O(14), and one O(6) atom to form AsO4 tetrahedra that share  a cornercorner with one Co(3)O6 octahedra,  a cornercorner with one Co(4)O6 octahedra, corners with two equivalent Co(1)O6 octahedra, corners with two equivalent Co(2)O6 octahedra, and corners with two equivalent As(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 44-64°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one As(2) and one As(4) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one As(1) and one As(3) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Co(3), one Co(4), and one As(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Co(3), one Co(4), one As(1), and one As(3) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Co(1), one Co(2), one As(2), and one As(4) atom. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Co(2), one Co(3), and one As(1) atom. In the eighth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Co(1), one Co(4), and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal non-coplanar geometry to one Co(1), one Co(4), and one As(1) atom. In the tenth O site, O(10) is bonded in a distorted trigonal non-coplanar geometry to one Co(2), one Co(3), and one As(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Co(2), one Co(3), and one As(3) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(4), and one As(4) atom. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Co(1), one Co(4), and one As(3) atom. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Co(2), one Co(3), and one As(4) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Co2As2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.812
_cell_length_b   5.326
_cell_length_c   5.366
_cell_angle_alpha   106.541
_cell_angle_beta   96.891
_cell_angle_gamma   97.161
_symmetry_Int_Tables_number   1
_cell_volume   129.042
_cell_formula_units_Z   1
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
  As  As0  1  0.100  0.746  0.743  1.0
  As  As1  1  0.902  0.220  0.222  1.0
  Co  Co2  1  0.494  0.687  0.311  1.0
  Co  Co3  1  0.491  0.312  0.701  1.0
  O  O4  1  0.082  0.030  0.007  1.0
  O  O5  1  0.750  0.620  0.626  1.0
  O  O6  1  0.197  0.423  0.426  1.0
  O  O7  1  0.282  0.926  0.580  1.0
  O  O8  1  0.283  0.589  0.927  1.0
  O  O9  1  0.705  0.391  0.069  1.0
  O  O10  1  0.713  0.056  0.387  1.0
[/CIF]
.