The crystal structure described by Co2As2O7 crystallizes in the triclinic P1 space group. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted CoO6 pentagonal pyramids that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with three equivalent Co(2)O6 pentagonal pyramids. In the second Co site, Co(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted CoO6 pentagonal pyramids that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with three equivalent Co(1)O6 pentagonal pyramids. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form AsO4 tetrahedra that share corners with three equivalent Co(1)O6 pentagonal pyramids, corners with three equivalent Co(2)O6 pentagonal 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(3), one O(6), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Co(1)O6 pentagonal pyramids, corners with three equivalent Co(2)O6 pentagonal pyramids, and  a cornercorner with one As(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one As(1) and one As(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Co(1), one Co(2), and one As(2) 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(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Co2As2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.858
_cell_length_b   5.444
_cell_length_c   5.459
_cell_angle_alpha   105.556
_cell_angle_beta   97.211
_cell_angle_gamma   97.442
_symmetry_Int_Tables_number   1
_cell_volume   135.974
_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  0.759  0.762  1.0
  As  As1  1  0.900  0.239  0.235  1.0
  Co  Co2  1  0.501  0.693  0.310  1.0
  Co  Co3  1  0.498  0.307  0.691  1.0
  O  O4  1  0.007  0.003  1.000  1.0
  O  O5  1  0.772  0.596  0.598  1.0
  O  O6  1  0.224  0.407  0.405  1.0
  O  O7  1  0.294  0.928  0.599  1.0
  O  O8  1  0.289  0.594  0.930  1.0
  O  O9  1  0.710  0.405  0.070  1.0
  O  O10  1  0.706  0.070  0.398  1.0
[/CIF]
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The crystal structure described by Co2As2O7 crystallizes in the triclinic P1 space group. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted CoO6 pentagonal pyramids that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with three equivalent Co(2)O6 pentagonal pyramids. In the second Co site, Co(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted CoO6 pentagonal pyramids that share corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra, and edges with three equivalent Co(1)O6 pentagonal pyramids. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form AsO4 tetrahedra that share corners with three equivalent Co(1)O6 pentagonal pyramids, corners with three equivalent Co(2)O6 pentagonal 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(3), one O(6), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Co(1)O6 pentagonal pyramids, corners with three equivalent Co(2)O6 pentagonal pyramids, and  a cornercorner with one As(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one As(1) and one As(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Co(1), one Co(2), and one As(2) 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(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Co2As2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.858
_cell_length_b   5.444
_cell_length_c   5.459
_cell_angle_alpha   105.556
_cell_angle_beta   97.211
_cell_angle_gamma   97.442
_symmetry_Int_Tables_number   1
_cell_volume   135.974
_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  0.759  0.762  1.0
  As  As1  1  0.900  0.239  0.235  1.0
  Co  Co2  1  0.501  0.693  0.310  1.0
  Co  Co3  1  0.498  0.307  0.691  1.0
  O  O4  1  0.007  0.003  1.000  1.0
  O  O5  1  0.772  0.596  0.598  1.0
  O  O6  1  0.224  0.407  0.405  1.0
  O  O7  1  0.294  0.928  0.599  1.0
  O  O8  1  0.289  0.594  0.930  1.0
  O  O9  1  0.710  0.405  0.070  1.0
  O  O10  1  0.706  0.070  0.398  1.0
[/CIF]
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