Co3(AsO4)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(4), one O(5), one O(8), and two equivalent O(7) atoms to form CoO6 octahedra that share  a cornercorner with one Co(3)O6 octahedra, corners with two equivalent Co(2)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-62°. In the second Co site, Co(2) is bonded to one O(3), one O(5), one O(6), one O(8), and two equivalent O(2) atoms to form CoO6 octahedra that share  a cornercorner with one Co(3)O6 octahedra, corners with two equivalent Co(1)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and  an edgeedge with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-55°. In the third Co site, Co(3) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form CoO6 octahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, and  an edgeedge with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-62°. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(2)O6 octahedra, and corners with three equivalent Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-60°. In the second As site, As(2) is bonded to one O(4), one O(5), one O(6), and one O(8) atom to form AsO4 tetrahedra that share  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Co(3)O6 octahedra, corners with three equivalent Co(1)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, and  an edgeedge with one Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-59°. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Co(1) and one As(1) atom. In the second O site, O(8) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(2) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one As(1) atom. In the fourth O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Co(3), two equivalent Co(2), and one As(1) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Co(2), one Co(3), and one As(1) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one As(2) atom. In the seventh O site, O(5) is bonded in a distorted trigonal pyramidal geometry to one Co(1), one Co(2), one Co(3), and one As(2) atom. In the eighth O site, O(6) is bonded in a distorted trigonal planar geometry to one Co(2), one Co(3), and one As(2) atom.
Co3(AsO4)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(4), one O(5), one O(8), and two equivalent O(7) atoms to form CoO6 octahedra that share  a cornercorner with one Co(3)O6 octahedra, corners with two equivalent Co(2)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-62°. The Co(1)-O(1) bond length is 2.09 Å. The Co(1)-O(4) bond length is 2.08 Å. The Co(1)-O(5) bond length is 2.11 Å. The Co(1)-O(8) bond length is 1.99 Å. There is one shorter (2.12 Å) and one longer (2.14 Å) Co(1)-O(7) bond length. In the second Co site, Co(2) is bonded to one O(3), one O(5), one O(6), one O(8), and two equivalent O(2) atoms to form CoO6 octahedra that share  a cornercorner with one Co(3)O6 octahedra, corners with two equivalent Co(1)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Co(2)O6 octahedra, edges with two equivalent Co(3)O6 octahedra, and  an edgeedge with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 53-55°. The Co(2)-O(3) bond length is 2.08 Å. The Co(2)-O(5) bond length is 2.26 Å. The Co(2)-O(6) bond length is 2.00 Å. The Co(2)-O(8) bond length is 2.03 Å. There is one shorter (2.12 Å) and one longer (2.15 Å) Co(2)-O(2) bond length. In the third Co site, Co(3) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form CoO6 octahedra that share  a cornercorner with one Co(1)O6 octahedra,  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one As(2)O4 tetrahedra, corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, edges with two equivalent Co(2)O6 octahedra, and  an edgeedge with one As(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-62°. The Co(3)-O(1) bond length is 2.05 Å. The Co(3)-O(2) bond length is 2.27 Å. The Co(3)-O(3) bond length is 2.05 Å. The Co(3)-O(4) bond length is 2.05 Å. The Co(3)-O(5) bond length is 2.10 Å. The Co(3)-O(6) bond length is 2.09 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form AsO4 tetrahedra that share corners with three equivalent Co(1)O6 octahedra, corners with three equivalent Co(2)O6 octahedra, and corners with three equivalent Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-60°. The As(1)-O(1) bond length is 1.71 Å. The As(1)-O(2) bond length is 1.74 Å. The As(1)-O(3) bond length is 1.71 Å. The As(1)-O(7) bond length is 1.71 Å. In the second As site, As(2) is bonded to one O(4), one O(5), one O(6), and one O(8) atom to form AsO4 tetrahedra that share  a cornercorner with one Co(2)O6 octahedra,  a cornercorner with one Co(3)O6 octahedra, corners with three equivalent Co(1)O6 octahedra,  an edgeedge with one Co(2)O6 octahedra, and  an edgeedge with one Co(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-59°. The As(2)-O(4) bond length is 1.69 Å. The As(2)-O(5) bond length is 1.74 Å. The As(2)-O(6) bond length is 1.71 Å. The As(2)-O(8) bond length is 1.71 Å. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Co(1) and one As(1) atom. In the second O site, O(8) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(2), and one As(2) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one As(1) atom. In the fourth O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Co(3), two equivalent Co(2), and one As(1) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to one Co(2), one Co(3), and one As(1) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Co(1), one Co(3), and one As(2) atom. In the seventh O site, O(5) is bonded in a distorted trigonal pyramidal geometry to one Co(1), one Co(2), one Co(3), and one As(2) atom. In the eighth O site, O(6) is bonded in a distorted trigonal planar geometry to one Co(2), one Co(3), and one As(2) atom.