Ti4(Ni5O8)3 crystallizes in the trigonal P-3m1 space group. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(6) and three equivalent O(1) atoms to form TiO4 tetrahedra that share corners with three equivalent Ni(3)O6 octahedra, corners with three equivalent Ni(5)O6 octahedra, and corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-57°. In the second Ti site, Ti(2) is bonded to one O(3) and three equivalent O(5) atoms to form TiO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with six equivalent Ni(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-56°. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form NiO6 octahedra that share corners with three equivalent Ni(2)O6 octahedra,  a cornercorner with one Ti(2)O4 tetrahedra, corners with two equivalent Ti(1)O4 tetrahedra,  an edgeedge with one Ni(3)O6 octahedra,  an edgeedge with one Ni(4)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-11°. In the second Ni site, Ni(2) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form a mixture of edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-11°. In the third Ni site, Ni(3) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form NiO6 octahedra that share corners with three equivalent Ti(1)O4 tetrahedra, corners with three equivalent Ti(2)O4 tetrahedra, edges with three equivalent Ni(1)O6 octahedra, and edges with three equivalent Ni(5)O6 octahedra. In the fourth Ni site, Ni(4) is bonded to six equivalent O(2) atoms to form edge-sharing NiO6 octahedra. In the fifth Ni site, Ni(5) is bonded to two equivalent O(6) and four equivalent O(5) atoms to form NiO6 octahedra that share corners with two equivalent Ti(1)O4 tetrahedra, corners with four equivalent Ti(2)O4 tetrahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with four equivalent Ni(5)O6 octahedra. There are six inequivalent O sites. In the first O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ti(2), one Ni(3), and two equivalent Ni(5) atoms. In the second O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Ti(1) and three equivalent Ni(5) atoms. In the third O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Ti(1), one Ni(3), and two equivalent Ni(1) atoms. In the fourth O site, O(2) is bonded to one Ni(4), two equivalent Ni(1), and two equivalent Ni(2) atoms to form ONi5 square pyramids that share corners with five equivalent O(2)Ni5 square pyramids, edges with three equivalent O(4)Ni6 octahedra, and edges with four equivalent O(2)Ni5 square pyramids. In the fifth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Ti(2) and three equivalent Ni(1) atoms. In the sixth O site, O(4) is bonded to three equivalent Ni(1) and three equivalent Ni(2) atoms to form ONi6 octahedra that share corners with three equivalent O(4)Ni6 octahedra and edges with nine equivalent O(2)Ni5 square pyramids. The corner-sharing octahedra are not tilted.
Ti4(Ni5O8)3 crystallizes in the trigonal P-3m1 space group. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(6) and three equivalent O(1) atoms to form TiO4 tetrahedra that share corners with three equivalent Ni(3)O6 octahedra, corners with three equivalent Ni(5)O6 octahedra, and corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-57°. The Ti(1)-O(6) bond length is 1.85 Å. All Ti(1)-O(1) bond lengths are 1.84 Å. In the second Ti site, Ti(2) is bonded to one O(3) and three equivalent O(5) atoms to form TiO4 tetrahedra that share corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(3)O6 octahedra, and corners with six equivalent Ni(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-56°. The Ti(2)-O(3) bond length is 1.84 Å. All Ti(2)-O(5) bond lengths are 1.85 Å. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form NiO6 octahedra that share corners with three equivalent Ni(2)O6 octahedra,  a cornercorner with one Ti(2)O4 tetrahedra, corners with two equivalent Ti(1)O4 tetrahedra,  an edgeedge with one Ni(3)O6 octahedra,  an edgeedge with one Ni(4)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and edges with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-11°. The Ni(1)-O(3) bond length is 2.04 Å. The Ni(1)-O(4) bond length is 2.10 Å. Both Ni(1)-O(1) bond lengths are 2.04 Å. Both Ni(1)-O(2) bond lengths are 2.09 Å. In the second Ni site, Ni(2) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form a mixture of edge and corner-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-11°. Both Ni(2)-O(4) bond lengths are 2.08 Å. All Ni(2)-O(2) bond lengths are 2.09 Å. In the third Ni site, Ni(3) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form NiO6 octahedra that share corners with three equivalent Ti(1)O4 tetrahedra, corners with three equivalent Ti(2)O4 tetrahedra, edges with three equivalent Ni(1)O6 octahedra, and edges with three equivalent Ni(5)O6 octahedra. All Ni(3)-O(1) bond lengths are 2.06 Å. All Ni(3)-O(5) bond lengths are 2.06 Å. In the fourth Ni site, Ni(4) is bonded to six equivalent O(2) atoms to form edge-sharing NiO6 octahedra. All Ni(4)-O(2) bond lengths are 1.88 Å. In the fifth Ni site, Ni(5) is bonded to two equivalent O(6) and four equivalent O(5) atoms to form NiO6 octahedra that share corners with two equivalent Ti(1)O4 tetrahedra, corners with four equivalent Ti(2)O4 tetrahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with four equivalent Ni(5)O6 octahedra. Both Ni(5)-O(6) bond lengths are 2.07 Å. All Ni(5)-O(5) bond lengths are 2.05 Å. There are six inequivalent O sites. In the first O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Ti(2), one Ni(3), and two equivalent Ni(5) atoms. In the second O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Ti(1) and three equivalent Ni(5) atoms. In the third O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Ti(1), one Ni(3), and two equivalent Ni(1) atoms. In the fourth O site, O(2) is bonded to one Ni(4), two equivalent Ni(1), and two equivalent Ni(2) atoms to form ONi5 square pyramids that share corners with five equivalent O(2)Ni5 square pyramids, edges with three equivalent O(4)Ni6 octahedra, and edges with four equivalent O(2)Ni5 square pyramids. In the fifth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Ti(2) and three equivalent Ni(1) atoms. In the sixth O site, O(4) is bonded to three equivalent Ni(1) and three equivalent Ni(2) atoms to form ONi6 octahedra that share corners with three equivalent O(4)Ni6 octahedra and edges with nine equivalent O(2)Ni5 square pyramids. The corner-sharing octahedra are not tilted.