Mo3Ni2O8 crystallizes in the hexagonal P6_3mc space group. Mo(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MoO6 octahedra that share corners with two equivalent Ni(2)O6 octahedra, corners with three equivalent Ni(1)O4 tetrahedra,  an edgeedge with one Ni(2)O6 octahedra, and edges with four equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 42°. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(4) and three equivalent O(1) atoms to form NiO4 tetrahedra that share corners with three equivalent Ni(2)O6 octahedra and corners with nine equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-67°. In the second Ni site, Ni(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Mo(1)O6 octahedra, corners with three equivalent Ni(1)O4 tetrahedra, and edges with three equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 42°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mo(1), one Ni(1), and one Ni(2) atom to form ONi2Mo2 tetrahedra that share  a cornercorner with one O(4)NiMo3 tetrahedra, corners with two equivalent O(1)Ni2Mo2 tetrahedra,  an edgeedge with one O(4)NiMo3 tetrahedra, and edges with two equivalent O(1)Ni2Mo2 tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Mo(1) and one Ni(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to three equivalent Mo(1) atoms. In the fourth O site, O(4) is bonded to three equivalent Mo(1) and one Ni(1) atom to form a mixture of distorted corner and edge-sharing ONiMo3 tetrahedra.
Mo3Ni2O8 crystallizes in the hexagonal P6_3mc space group. Mo(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MoO6 octahedra that share corners with two equivalent Ni(2)O6 octahedra, corners with three equivalent Ni(1)O4 tetrahedra,  an edgeedge with one Ni(2)O6 octahedra, and edges with four equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 42°. The Mo(1)-O(3) bond length is 2.06 Å. The Mo(1)-O(4) bond length is 2.16 Å. Both Mo(1)-O(1) bond lengths are 2.11 Å. Both Mo(1)-O(2) bond lengths are 1.99 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(4) and three equivalent O(1) atoms to form NiO4 tetrahedra that share corners with three equivalent Ni(2)O6 octahedra and corners with nine equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-67°. The Ni(1)-O(4) bond length is 1.99 Å. All Ni(1)-O(1) bond lengths are 1.98 Å. In the second Ni site, Ni(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent Mo(1)O6 octahedra, corners with three equivalent Ni(1)O4 tetrahedra, and edges with three equivalent Mo(1)O6 octahedra. The corner-sharing octahedral tilt angles are 42°. All Ni(2)-O(1) bond lengths are 2.15 Å. All Ni(2)-O(2) bond lengths are 2.05 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mo(1), one Ni(1), and one Ni(2) atom to form ONi2Mo2 tetrahedra that share  a cornercorner with one O(4)NiMo3 tetrahedra, corners with two equivalent O(1)Ni2Mo2 tetrahedra,  an edgeedge with one O(4)NiMo3 tetrahedra, and edges with two equivalent O(1)Ni2Mo2 tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Mo(1) and one Ni(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to three equivalent Mo(1) atoms. In the fourth O site, O(4) is bonded to three equivalent Mo(1) and one Ni(1) atom to form a mixture of distorted corner and edge-sharing ONiMo3 tetrahedra.