Ni5(AsO6)2 crystallizes in the monoclinic C2/m space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(3)O6 octahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra,  an edgeedge with one Ni(2)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. In the third Ni site, Ni(3) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent As(1)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. As(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ni(3)O6 octahedra, corners with four equivalent Ni(1)O6 octahedra, and corners with four equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-56°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one As(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Ni(3), two equivalent Ni(1), and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ni(2) and one As(1) atom. In the fourth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Ni(1), one Ni(2), and one Ni(3) atom.
Ni5(AsO6)2 crystallizes in the monoclinic C2/m space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with two equivalent Ni(3)O6 octahedra. Both Ni(1)-O(1) bond lengths are 2.05 Å. Both Ni(1)-O(2) bond lengths are 2.09 Å. Both Ni(1)-O(4) bond lengths are 1.93 Å. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra,  an edgeedge with one Ni(2)O6 octahedra,  an edgeedge with one Ni(3)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. Both Ni(2)-O(1) bond lengths are 2.16 Å. Both Ni(2)-O(3) bond lengths are 2.02 Å. Both Ni(2)-O(4) bond lengths are 1.91 Å. In the third Ni site, Ni(3) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent As(1)O4 tetrahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. Both Ni(3)-O(2) bond lengths are 2.21 Å. All Ni(3)-O(4) bond lengths are 1.89 Å. As(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form AsO4 tetrahedra that share  a cornercorner with one Ni(3)O6 octahedra, corners with four equivalent Ni(1)O6 octahedra, and corners with four equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-56°. The As(1)-O(2) bond length is 1.76 Å. The As(1)-O(3) bond length is 1.75 Å. Both As(1)-O(1) bond lengths are 1.72 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one As(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Ni(3), two equivalent Ni(1), and one As(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ni(2) and one As(1) atom. In the fourth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Ni(1), one Ni(2), and one Ni(3) atom.