Ba4Nd(IrO4)3 crystallizes in the monoclinic C2/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 11-coordinate geometry to two equivalent O(4), three equivalent O(3), and six equivalent O(1) atoms. In the second Ba site, Ba(2) is bonded to one O(3), two equivalent O(1), three equivalent O(2), and six equivalent O(4) atoms to form distorted BaO12 cuboctahedra that share corners with six equivalent Ba(2)O12 cuboctahedra, corners with three equivalent Ir(2)O6 octahedra, faces with three equivalent Ba(2)O12 cuboctahedra, faces with three equivalent Nd(1)O6 octahedra, and faces with four equivalent Ir(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 10-19°. Nd(1) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form NdO6 octahedra that share corners with six equivalent Ir(1)O6 octahedra and faces with six equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 11-14°. There are two inequivalent Ir sites. In the first Ir site, Ir(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form IrO6 octahedra that share corners with three equivalent Nd(1)O6 octahedra, faces with four equivalent Ba(2)O12 cuboctahedra, and  a faceface with one Ir(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-14°. In the second Ir site, Ir(2) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form IrO6 octahedra that share corners with six equivalent Ba(2)O12 cuboctahedra and faces with two equivalent Ir(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one Ir(1), and one Ir(2) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to three equivalent Ba(2), one Nd(1), and one Ir(1) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one Ir(1), and one Ir(2) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Ba(1), three equivalent Ba(2), one Nd(1), and one Ir(1) atom.
Ba4Nd(IrO4)3 crystallizes in the monoclinic C2/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 11-coordinate geometry to two equivalent O(4), three equivalent O(3), and six equivalent O(1) atoms. Both Ba(1)-O(4) bond lengths are 2.94 Å. There is one shorter (2.77 Å) and two longer (3.00 Å) Ba(1)-O(3) bond lengths. There are a spread of Ba(1)-O(1) bond distances ranging from 2.94-3.14 Å. In the second Ba site, Ba(2) is bonded to one O(3), two equivalent O(1), three equivalent O(2), and six equivalent O(4) atoms to form distorted BaO12 cuboctahedra that share corners with six equivalent Ba(2)O12 cuboctahedra, corners with three equivalent Ir(2)O6 octahedra, faces with three equivalent Ba(2)O12 cuboctahedra, faces with three equivalent Nd(1)O6 octahedra, and faces with four equivalent Ir(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 10-19°. The Ba(2)-O(3) bond length is 3.16 Å. Both Ba(2)-O(1) bond lengths are 2.82 Å. There is one shorter (2.98 Å) and two longer (3.04 Å) Ba(2)-O(2) bond lengths. There are a spread of Ba(2)-O(4) bond distances ranging from 2.88-3.41 Å. Nd(1) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form NdO6 octahedra that share corners with six equivalent Ir(1)O6 octahedra and faces with six equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 11-14°. Both Nd(1)-O(2) bond lengths are 2.32 Å. All Nd(1)-O(4) bond lengths are 2.30 Å. There are two inequivalent Ir sites. In the first Ir site, Ir(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form IrO6 octahedra that share corners with three equivalent Nd(1)O6 octahedra, faces with four equivalent Ba(2)O12 cuboctahedra, and  a faceface with one Ir(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-14°. The Ir(1)-O(2) bond length is 1.97 Å. The Ir(1)-O(3) bond length is 2.07 Å. Both Ir(1)-O(1) bond lengths are 2.08 Å. Both Ir(1)-O(4) bond lengths are 1.97 Å. In the second Ir site, Ir(2) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form IrO6 octahedra that share corners with six equivalent Ba(2)O12 cuboctahedra and faces with two equivalent Ir(1)O6 octahedra. Both Ir(2)-O(3) bond lengths are 2.04 Å. All Ir(2)-O(1) bond lengths are 2.05 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one Ir(1), and one Ir(2) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to three equivalent Ba(2), one Nd(1), and one Ir(1) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one Ir(1), and one Ir(2) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Ba(1), three equivalent Ba(2), one Nd(1), and one Ir(1) atom.