Ni3(AsO4)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(3), one O(5), one O(7), one O(8), and two equivalent O(1) atoms to form NiO6 octahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, and  an edgeedge with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-60°. In the second Ni site, Ni(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 NiO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and  an edgeedge with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-60°. In the third Ni site, Ni(3) is bonded to one O(2), one O(6), one O(7), one O(8), and two equivalent O(4) atoms to form NiO6 octahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Ni(3)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and  an edgeedge with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-55°. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form AsO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, and  an edgeedge with one Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-60°. In the second As site, As(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra, and corners with three equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-61°. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ni(2), two equivalent Ni(3), and one As(2) atom. In the second O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one As(1) atom. In the third O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one As(1) atom. In the fourth O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Ni(1), one Ni(2), one Ni(3), and one As(1) atom. In the fifth O site, O(8) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(3), and one As(1) atom. In the sixth O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one As(2) atom. In the seventh O site, O(2) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one As(2) atom. In the eighth O site, O(3) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one As(2) atom.
Ni3(AsO4)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(3), one O(5), one O(7), one O(8), and two equivalent O(1) atoms to form NiO6 octahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(3)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, and  an edgeedge with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-60°. The Ni(1)-O(3) bond length is 2.06 Å. The Ni(1)-O(5) bond length is 2.04 Å. The Ni(1)-O(7) bond length is 2.06 Å. The Ni(1)-O(8) bond length is 1.98 Å. There is one shorter (2.11 Å) and one longer (2.12 Å) Ni(1)-O(1) bond length. In the second Ni site, Ni(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 NiO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and  an edgeedge with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-60°. The Ni(2)-O(2) bond length is 2.03 Å. The Ni(2)-O(3) bond length is 2.04 Å. The Ni(2)-O(4) bond length is 2.20 Å. The Ni(2)-O(5) bond length is 2.02 Å. The Ni(2)-O(6) bond length is 2.04 Å. The Ni(2)-O(7) bond length is 2.08 Å. In the third Ni site, Ni(3) is bonded to one O(2), one O(6), one O(7), one O(8), and two equivalent O(4) atoms to form NiO6 octahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra,  a cornercorner with one As(1)O4 tetrahedra, corners with three equivalent As(2)O4 tetrahedra,  an edgeedge with one Ni(3)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and  an edgeedge with one As(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 52-55°. The Ni(3)-O(2) bond length is 2.04 Å. The Ni(3)-O(6) bond length is 1.99 Å. The Ni(3)-O(7) bond length is 2.19 Å. The Ni(3)-O(8) bond length is 2.02 Å. There is one shorter (2.07 Å) and one longer (2.12 Å) Ni(3)-O(4) bond length. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form AsO4 tetrahedra that share  a cornercorner with one Ni(2)O6 octahedra,  a cornercorner with one Ni(3)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, and  an edgeedge with one Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-60°. The As(1)-O(5) bond length is 1.69 Å. The As(1)-O(6) bond length is 1.71 Å. The As(1)-O(7) bond length is 1.75 Å. The As(1)-O(8) bond length is 1.70 Å. In the second As site, As(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra, and corners with three equivalent Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-61°. The As(2)-O(1) bond length is 1.71 Å. The As(2)-O(2) bond length is 1.71 Å. The As(2)-O(3) bond length is 1.71 Å. The As(2)-O(4) bond length is 1.75 Å. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ni(2), two equivalent Ni(3), and one As(2) atom. In the second O site, O(5) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one As(1) atom. In the third O site, O(6) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one As(1) atom. In the fourth O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Ni(1), one Ni(2), one Ni(3), and one As(1) atom. In the fifth O site, O(8) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(3), and one As(1) atom. In the sixth O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one As(2) atom. In the seventh O site, O(2) is bonded in a distorted trigonal planar geometry to one Ni(2), one Ni(3), and one As(2) atom. In the eighth O site, O(3) is bonded in a distorted trigonal planar geometry to one Ni(1), one Ni(2), and one As(2) atom.