Ni5O7 crystallizes in the orthorhombic Cmcm space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 2-12°. In the second Ni site, Ni(2) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form a mixture of corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 5°. In the third Ni site, Ni(3) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 2-58°. There are four inequivalent O sites. In the first O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Ni(3) atoms. In the second O site, O(1) is bonded to one Ni(3), two equivalent Ni(2), and three equivalent Ni(1) atoms to form ONi6 octahedra that share corners with two equivalent O(1)Ni6 octahedra, corners with two equivalent O(3)Ni5 square pyramids, edges with five equivalent O(1)Ni6 octahedra, and edges with five equivalent O(3)Ni5 square pyramids. The corner-sharing octahedra are not tilted. In the third O site, O(2) is bonded in a trigonal non-coplanar geometry to one Ni(1) and two equivalent Ni(3) atoms. In the fourth O site, O(3) is bonded to one Ni(2), two equivalent Ni(1), and two equivalent Ni(3) atoms to form ONi5 square pyramids that share corners with two equivalent O(1)Ni6 octahedra,  a cornercorner with one O(3)Ni5 square pyramid, edges with five equivalent O(1)Ni6 octahedra, and edges with two equivalent O(3)Ni5 square pyramids. The corner-sharing octahedral tilt angles are 9°.
Ni5O7 crystallizes in the orthorhombic Cmcm space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), two equivalent O(3), and three equivalent O(1) atoms to form a mixture of corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 2-12°. The Ni(1)-O(2) bond length is 1.97 Å. Both Ni(1)-O(3) bond lengths are 2.08 Å. There are two shorter (2.08 Å) and one longer (2.13 Å) Ni(1)-O(1) bond length. In the second Ni site, Ni(2) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form a mixture of corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 5°. Both Ni(2)-O(3) bond lengths are 2.00 Å. All Ni(2)-O(1) bond lengths are 2.08 Å. In the third Ni site, Ni(3) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 2-58°. The Ni(3)-O(1) bond length is 2.28 Å. The Ni(3)-O(4) bond length is 1.87 Å. Both Ni(3)-O(2) bond lengths are 1.92 Å. Both Ni(3)-O(3) bond lengths are 2.04 Å. There are four inequivalent O sites. In the first O site, O(4) is bonded in a bent 120 degrees geometry to two equivalent Ni(3) atoms. In the second O site, O(1) is bonded to one Ni(3), two equivalent Ni(2), and three equivalent Ni(1) atoms to form ONi6 octahedra that share corners with two equivalent O(1)Ni6 octahedra, corners with two equivalent O(3)Ni5 square pyramids, edges with five equivalent O(1)Ni6 octahedra, and edges with five equivalent O(3)Ni5 square pyramids. The corner-sharing octahedra are not tilted. In the third O site, O(2) is bonded in a trigonal non-coplanar geometry to one Ni(1) and two equivalent Ni(3) atoms. In the fourth O site, O(3) is bonded to one Ni(2), two equivalent Ni(1), and two equivalent Ni(3) atoms to form ONi5 square pyramids that share corners with two equivalent O(1)Ni6 octahedra,  a cornercorner with one O(3)Ni5 square pyramid, edges with five equivalent O(1)Ni6 octahedra, and edges with two equivalent O(3)Ni5 square pyramids. The corner-sharing octahedral tilt angles are 9°.