V4Ni2O9 is Ilmenite-like structured and crystallizes in the monoclinic Cc space group. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(9) atom to form VO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent V(4)O6 octahedra, corners with three equivalent V(2)O6 octahedra, corners with three equivalent V(3)O6 octahedra,  an edgeedge with one Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and  a faceface with one V(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-59°. In the second V site, V(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form distorted VO6 octahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(3)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, edges with two equivalent V(4)O6 octahedra, and  a faceface with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-62°. In the third V site, V(3) is bonded to one O(1), one O(2), one O(4), one O(7), one O(8), and one O(9) atom to form VO6 octahedra that share  a cornercorner with one V(4)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(2)O6 octahedra,  an edgeedge with one V(4)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and  a faceface with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-63°. In the fourth V site, V(4) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(9) atom to form VO6 octahedra that share  a cornercorner with one V(3)O6 octahedra, corners with two equivalent V(1)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra,  an edgeedge with one V(3)O6 octahedra, edges with two equivalent V(2)O6 octahedra, and  a faceface with one V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-59°. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NiO6 octahedra that share  a cornercorner with one V(1)O6 octahedra, corners with two equivalent V(2)O6 octahedra, corners with three equivalent V(4)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra,  an edgeedge with one V(1)O6 octahedra, edges with two equivalent V(3)O6 octahedra, and  a faceface with one V(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-62°. In the second Ni site, Ni(2) is bonded to one O(1), one O(3), one O(4), one O(7), one O(8), and one O(9) atom to form distorted NiO6 octahedra that share  a cornercorner with one V(2)O6 octahedra, corners with two equivalent V(3)O6 octahedra, corners with three equivalent V(4)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra,  an edgeedge with one V(2)O6 octahedra, edges with two equivalent V(1)O6 octahedra, and  a faceface with one V(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-63°. There are nine inequivalent O sites. In the first O site, O(7) is bonded in a distorted see-saw-like geometry to one V(1), one V(3), one Ni(1), and one Ni(2) atom. In the second O site, O(8) is bonded in a rectangular see-saw-like geometry to one V(2), one V(3), one Ni(1), and one Ni(2) atom. In the third O site, O(9) is bonded in a rectangular see-saw-like geometry to one V(1), one V(3), one V(4), and one Ni(2) atom. In the fourth O site, O(1) is bonded in a distorted see-saw-like geometry to one V(1), one V(3), one V(4), and one Ni(2) atom. In the fifth O site, O(2) is bonded in a distorted trigonal pyramidal geometry to one V(2), one V(3), one V(4), and one Ni(1) atom. In the sixth O site, O(3) is bonded in a rectangular see-saw-like geometry to one V(1), one V(2), one V(4), and one Ni(2) atom. In the seventh O site, O(4) is bonded in a distorted see-saw-like geometry to one V(2), one V(3), one Ni(1), and one Ni(2) atom. In the eighth O site, O(5) is bonded in a rectangular see-saw-like geometry to one V(1), one V(2), one V(4), and one Ni(1) atom. In the ninth O site, O(6) is bonded in a distorted see-saw-like geometry to one V(1), one V(2), one V(4), and one Ni(1) atom.
V4Ni2O9 is Ilmenite-like structured and crystallizes in the monoclinic Cc space group. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(9) atom to form VO6 octahedra that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent V(4)O6 octahedra, corners with three equivalent V(2)O6 octahedra, corners with three equivalent V(3)O6 octahedra,  an edgeedge with one Ni(1)O6 octahedra, edges with two equivalent Ni(2)O6 octahedra, and  a faceface with one V(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-59°. The V(1)-O(1) bond length is 2.00 Å. The V(1)-O(3) bond length is 2.10 Å. The V(1)-O(5) bond length is 1.90 Å. The V(1)-O(6) bond length is 2.12 Å. The V(1)-O(7) bond length is 1.91 Å. The V(1)-O(9) bond length is 1.94 Å. In the second V site, V(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form distorted VO6 octahedra that share  a cornercorner with one Ni(2)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(3)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, edges with two equivalent V(4)O6 octahedra, and  a faceface with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-62°. The V(2)-O(2) bond length is 2.04 Å. The V(2)-O(3) bond length is 1.98 Å. The V(2)-O(4) bond length is 2.01 Å. The V(2)-O(5) bond length is 2.17 Å. The V(2)-O(6) bond length is 1.96 Å. The V(2)-O(8) bond length is 1.82 Å. In the third V site, V(3) is bonded to one O(1), one O(2), one O(4), one O(7), one O(8), and one O(9) atom to form VO6 octahedra that share  a cornercorner with one V(4)O6 octahedra, corners with two equivalent Ni(2)O6 octahedra, corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(2)O6 octahedra,  an edgeedge with one V(4)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and  a faceface with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 40-63°. The V(3)-O(1) bond length is 2.02 Å. The V(3)-O(2) bond length is 2.02 Å. The V(3)-O(4) bond length is 1.96 Å. The V(3)-O(7) bond length is 2.08 Å. The V(3)-O(8) bond length is 2.12 Å. The V(3)-O(9) bond length is 2.08 Å. In the fourth V site, V(4) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(9) atom to form VO6 octahedra that share  a cornercorner with one V(3)O6 octahedra, corners with two equivalent V(1)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra,  an edgeedge with one V(3)O6 octahedra, edges with two equivalent V(2)O6 octahedra, and  a faceface with one V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-59°. The V(4)-O(1) bond length is 2.07 Å. The V(4)-O(2) bond length is 1.97 Å. The V(4)-O(3) bond length is 2.09 Å. The V(4)-O(5) bond length is 2.05 Å. The V(4)-O(6) bond length is 2.08 Å. The V(4)-O(9) bond length is 2.01 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form distorted NiO6 octahedra that share  a cornercorner with one V(1)O6 octahedra, corners with two equivalent V(2)O6 octahedra, corners with three equivalent V(4)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra,  an edgeedge with one V(1)O6 octahedra, edges with two equivalent V(3)O6 octahedra, and  a faceface with one V(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-62°. The Ni(1)-O(2) bond length is 2.13 Å. The Ni(1)-O(4) bond length is 2.10 Å. The Ni(1)-O(5) bond length is 2.17 Å. The Ni(1)-O(6) bond length is 2.04 Å. The Ni(1)-O(7) bond length is 2.04 Å. The Ni(1)-O(8) bond length is 2.06 Å. In the second Ni site, Ni(2) is bonded to one O(1), one O(3), one O(4), one O(7), one O(8), and one O(9) atom to form distorted NiO6 octahedra that share  a cornercorner with one V(2)O6 octahedra, corners with two equivalent V(3)O6 octahedra, corners with three equivalent V(4)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra,  an edgeedge with one V(2)O6 octahedra, edges with two equivalent V(1)O6 octahedra, and  a faceface with one V(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-63°. The Ni(2)-O(1) bond length is 2.05 Å. The Ni(2)-O(3) bond length is 2.03 Å. The Ni(2)-O(4) bond length is 2.05 Å. The Ni(2)-O(7) bond length is 2.12 Å. The Ni(2)-O(8) bond length is 2.19 Å. The Ni(2)-O(9) bond length is 2.17 Å. There are nine inequivalent O sites. In the first O site, O(7) is bonded in a distorted see-saw-like geometry to one V(1), one V(3), one Ni(1), and one Ni(2) atom. In the second O site, O(8) is bonded in a rectangular see-saw-like geometry to one V(2), one V(3), one Ni(1), and one Ni(2) atom. In the third O site, O(9) is bonded in a rectangular see-saw-like geometry to one V(1), one V(3), one V(4), and one Ni(2) atom. In the fourth O site, O(1) is bonded in a distorted see-saw-like geometry to one V(1), one V(3), one V(4), and one Ni(2) atom. In the fifth O site, O(2) is bonded in a distorted trigonal pyramidal geometry to one V(2), one V(3), one V(4), and one Ni(1) atom. In the sixth O site, O(3) is bonded in a rectangular see-saw-like geometry to one V(1), one V(2), one V(4), and one Ni(2) atom. In the seventh O site, O(4) is bonded in a distorted see-saw-like geometry to one V(2), one V(3), one Ni(1), and one Ni(2) atom. In the eighth O site, O(5) is bonded in a rectangular see-saw-like geometry to one V(1), one V(2), one V(4), and one Ni(1) atom. In the ninth O site, O(6) is bonded in a distorted see-saw-like geometry to one V(1), one V(2), one V(4), and one Ni(1) atom.