Co2As2O5 crystallizes in the triclinic P-1 space group. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(10), one O(2), one O(3), one O(4), and one O(6) atom to form CoO5 trigonal bipyramids that share  a cornercorner with one Co(2)O4 tetrahedra,  an edgeedge with one Co(3)O6 octahedra, and  an edgeedge with one Co(4)O6 octahedra. In the second Co site, Co(2) is bonded to one O(6), one O(7), and two equivalent O(1) atoms to form distorted CoO4 tetrahedra that share  a cornercorner with one Co(3)O6 octahedra,  a cornercorner with one Co(4)O6 octahedra,  a cornercorner with one Co(1)O5 trigonal bipyramid, and  an edgeedge with one Co(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 68-74°. In the third Co site, Co(3) is bonded to one O(10), one O(2), one O(5), one O(7), and two equivalent O(9) atoms to form distorted CoO6 octahedra that share  a cornercorner with one Co(2)O4 tetrahedra,  an edgeedge with one Co(3)O6 octahedra, edges with three equivalent Co(4)O6 octahedra, and  an edgeedge with one Co(1)O5 trigonal bipyramid. In the fourth Co site, Co(4) is bonded to one O(10), one O(3), one O(7), one O(9), and two equivalent O(5) atoms to form CoO6 octahedra that share  a cornercorner with one Co(2)O4 tetrahedra,  an edgeedge with one Co(4)O6 octahedra, edges with three equivalent Co(3)O6 octahedra, and  an edgeedge with one Co(1)O5 trigonal bipyramid. There are four inequivalent As sites. In the first As site, As(1) is bonded in a distorted T-shaped geometry to one O(2), one O(3), and one O(4) atom. In the second As site, As(2) is bonded in a distorted trigonal non-coplanar geometry to one O(4), one O(5), and one O(8) atom. In the third As site, As(3) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(10), and one O(6) atom. In the fourth As site, As(4) is bonded in a distorted trigonal non-coplanar geometry to one O(7), one O(8), and one O(9) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Co(2) and one As(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(4), and one As(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Co(1), one As(1), and one As(2) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Co(3), two equivalent Co(4), and one As(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Co(1), one Co(2), and one As(3) atom. In the seventh O site, O(7) is bonded to one Co(2), one Co(3), one Co(4), and one As(4) atom to form a mixture of corner and edge-sharing OCo3As trigonal pyramids. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one As(2) and one As(4) atom. In the ninth O site, O(9) is bonded to one Co(4), two equivalent Co(3), and one As(4) atom to form a mixture of corner and edge-sharing OCo3As trigonal pyramids. In the tenth O site, O(10) is bonded in a rectangular see-saw-like geometry to one Co(1), one Co(3), one Co(4), and one As(3) atom.
Co2As2O5 crystallizes in the triclinic P-1 space group. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(10), one O(2), one O(3), one O(4), and one O(6) atom to form CoO5 trigonal bipyramids that share  a cornercorner with one Co(2)O4 tetrahedra,  an edgeedge with one Co(3)O6 octahedra, and  an edgeedge with one Co(4)O6 octahedra. The Co(1)-O(10) bond length is 2.12 Å. The Co(1)-O(2) bond length is 1.94 Å. The Co(1)-O(3) bond length is 1.95 Å. The Co(1)-O(4) bond length is 2.24 Å. The Co(1)-O(6) bond length is 1.99 Å. In the second Co site, Co(2) is bonded to one O(6), one O(7), and two equivalent O(1) atoms to form distorted CoO4 tetrahedra that share  a cornercorner with one Co(3)O6 octahedra,  a cornercorner with one Co(4)O6 octahedra,  a cornercorner with one Co(1)O5 trigonal bipyramid, and  an edgeedge with one Co(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 68-74°. The Co(2)-O(6) bond length is 1.97 Å. The Co(2)-O(7) bond length is 1.98 Å. There is one shorter (1.96 Å) and one longer (2.00 Å) Co(2)-O(1) bond length. In the third Co site, Co(3) is bonded to one O(10), one O(2), one O(5), one O(7), and two equivalent O(9) atoms to form distorted CoO6 octahedra that share  a cornercorner with one Co(2)O4 tetrahedra,  an edgeedge with one Co(3)O6 octahedra, edges with three equivalent Co(4)O6 octahedra, and  an edgeedge with one Co(1)O5 trigonal bipyramid. The Co(3)-O(10) bond length is 2.19 Å. The Co(3)-O(2) bond length is 1.99 Å. The Co(3)-O(5) bond length is 2.06 Å. The Co(3)-O(7) bond length is 2.15 Å. There is one shorter (2.05 Å) and one longer (2.22 Å) Co(3)-O(9) bond length. In the fourth Co site, Co(4) is bonded to one O(10), one O(3), one O(7), one O(9), and two equivalent O(5) atoms to form CoO6 octahedra that share  a cornercorner with one Co(2)O4 tetrahedra,  an edgeedge with one Co(4)O6 octahedra, edges with three equivalent Co(3)O6 octahedra, and  an edgeedge with one Co(1)O5 trigonal bipyramid. The Co(4)-O(10) bond length is 2.08 Å. The Co(4)-O(3) bond length is 2.06 Å. The Co(4)-O(7) bond length is 2.19 Å. The Co(4)-O(9) bond length is 2.13 Å. There is one shorter (2.07 Å) and one longer (2.11 Å) Co(4)-O(5) bond length. There are four inequivalent As sites. In the first As site, As(1) is bonded in a distorted T-shaped geometry to one O(2), one O(3), and one O(4) atom. The As(1)-O(2) bond length is 1.77 Å. The As(1)-O(3) bond length is 1.76 Å. The As(1)-O(4) bond length is 1.86 Å. In the second As site, As(2) is bonded in a distorted trigonal non-coplanar geometry to one O(4), one O(5), and one O(8) atom. The As(2)-O(4) bond length is 1.81 Å. The As(2)-O(5) bond length is 1.80 Å. The As(2)-O(8) bond length is 1.79 Å. In the third As site, As(3) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(10), and one O(6) atom. The As(3)-O(1) bond length is 1.79 Å. The As(3)-O(10) bond length is 1.80 Å. The As(3)-O(6) bond length is 1.79 Å. In the fourth As site, As(4) is bonded in a distorted trigonal non-coplanar geometry to one O(7), one O(8), and one O(9) atom. The As(4)-O(7) bond length is 1.82 Å. The As(4)-O(8) bond length is 1.78 Å. The As(4)-O(9) bond length is 1.81 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Co(2) and one As(3) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(4), and one As(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Co(1), one As(1), and one As(2) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Co(3), two equivalent Co(4), and one As(2) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Co(1), one Co(2), and one As(3) atom. In the seventh O site, O(7) is bonded to one Co(2), one Co(3), one Co(4), and one As(4) atom to form a mixture of corner and edge-sharing OCo3As trigonal pyramids. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one As(2) and one As(4) atom. In the ninth O site, O(9) is bonded to one Co(4), two equivalent Co(3), and one As(4) atom to form a mixture of corner and edge-sharing OCo3As trigonal pyramids. In the tenth O site, O(10) is bonded in a rectangular see-saw-like geometry to one Co(1), one Co(3), one Co(4), and one As(3) atom.