BaNi4AlO7 crystallizes in the hexagonal P6_3mc space group. Ba(1) is bonded to six equivalent O(1) and six equivalent O(3) atoms to form distorted BaO12 cuboctahedra that share corners with twelve equivalent Ba(1)O12 cuboctahedra, edges with three equivalent Ni(2)O4 tetrahedra, edges with nine equivalent Ni(1)O4 tetrahedra, and faces with four equivalent Al(1)O6 octahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form NiO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with two equivalent Ni(2)O4 tetrahedra, corners with four equivalent Ni(1)O4 tetrahedra, and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 48-54°. In the second Ni site, Ni(2) is bonded to one O(2) and three equivalent O(1) atoms to form NiO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with six equivalent Ni(1)O4 tetrahedra, and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 54°. Al(1) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form AlO6 octahedra that share corners with three equivalent Ni(2)O4 tetrahedra, corners with nine equivalent Ni(1)O4 tetrahedra, and faces with four equivalent Ba(1)O12 cuboctahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ba(1), one Ni(1), one Ni(2), and one Al(1) atom. In the second O site, O(2) is bonded in a tetrahedral geometry to one Ni(2) and three equivalent Ni(1) atoms. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ba(1), two equivalent Ni(1), and one Al(1) atom.
BaNi4AlO7 crystallizes in the hexagonal P6_3mc space group. Ba(1) is bonded to six equivalent O(1) and six equivalent O(3) atoms to form distorted BaO12 cuboctahedra that share corners with twelve equivalent Ba(1)O12 cuboctahedra, edges with three equivalent Ni(2)O4 tetrahedra, edges with nine equivalent Ni(1)O4 tetrahedra, and faces with four equivalent Al(1)O6 octahedra. All Ba(1)-O(1) bond lengths are 3.00 Å. There are three shorter (2.87 Å) and three longer (3.29 Å) Ba(1)-O(3) bond lengths. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form NiO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with two equivalent Ni(2)O4 tetrahedra, corners with four equivalent Ni(1)O4 tetrahedra, and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 48-54°. The Ni(1)-O(1) bond length is 1.98 Å. The Ni(1)-O(2) bond length is 1.93 Å. Both Ni(1)-O(3) bond lengths are 1.95 Å. In the second Ni site, Ni(2) is bonded to one O(2) and three equivalent O(1) atoms to form NiO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with six equivalent Ni(1)O4 tetrahedra, and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 54°. The Ni(2)-O(2) bond length is 1.86 Å. All Ni(2)-O(1) bond lengths are 1.90 Å. Al(1) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form AlO6 octahedra that share corners with three equivalent Ni(2)O4 tetrahedra, corners with nine equivalent Ni(1)O4 tetrahedra, and faces with four equivalent Ba(1)O12 cuboctahedra. All Al(1)-O(1) bond lengths are 2.06 Å. All Al(1)-O(3) bond lengths are 1.90 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ba(1), one Ni(1), one Ni(2), and one Al(1) atom. In the second O site, O(2) is bonded in a tetrahedral geometry to one Ni(2) and three equivalent Ni(1) atoms. In the third O site, O(3) is bonded in a 3-coordinate geometry to two equivalent Ba(1), two equivalent Ni(1), and one Al(1) atom.