Ba3ZrNb5O12 crystallizes in the tetragonal P4/nmm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to four equivalent O(4) and eight equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, corners with eight equivalent Ba(2)O12 cuboctahedra, faces with two equivalent Ba(2)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Zr(1)O6 octahedra, and faces with four equivalent Nb(4)O6 octahedra. In the second Ba site, Ba(2) is bonded to two equivalent O(2), two equivalent O(3), four equivalent O(1), and four equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, corners with four equivalent Ba(2)O12 cuboctahedra,  a faceface with one Ba(1)O12 cuboctahedra, faces with four equivalent Ba(2)O12 cuboctahedra, faces with two equivalent Zr(1)O6 octahedra, faces with two equivalent Nb(4)O6 octahedra, faces with two equivalent Nb(1)O5 square pyramids, and faces with two equivalent Nb(2)O5 square pyramids. Zr(1) is bonded to one O(3), one O(4), and four equivalent O(5) atoms to form ZrO6 octahedra that share corners with five equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(2)O5 square pyramid, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-3°. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2) and four equivalent O(1) atoms to form NbO5 square pyramids that share  a cornercorner with one Nb(4)O6 octahedra, corners with four equivalent Nb(2)O5 square pyramids, and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. In the second Nb site, Nb(2) is bonded to one O(3) and four equivalent O(1) atoms to form NbO5 square pyramids that share  a cornercorner with one Zr(1)O6 octahedra, corners with four equivalent Nb(1)O5 square pyramids, and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. In the third Nb site, Nb(3) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(6) atoms. In the fourth Nb site, Nb(4) is bonded to one O(2), one O(4), and four equivalent O(5) atoms to form NbO6 octahedra that share corners with five equivalent Zr(1)O6 octahedra,  a cornercorner with one Nb(1)O5 square pyramid, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-3°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Zr(1), and one Nb(4) atom. In the second O site, O(6) is bonded in a square co-planar geometry to four equivalent Nb(3) atoms. In the third O site, O(1) is bonded to two equivalent Ba(2), one Nb(1), one Nb(2), and one Nb(3) atom to form a mixture of distorted edge and corner-sharing OBa2Nb3 trigonal bipyramids. In the fourth O site, O(2) is bonded in a distorted linear geometry to four equivalent Ba(2), one Nb(1), and one Nb(4) atom. In the fifth O site, O(3) is bonded in a distorted linear geometry to four equivalent Ba(2), one Zr(1), and one Nb(2) atom. In the sixth O site, O(4) is bonded in a distorted linear geometry to four equivalent Ba(1), one Zr(1), and one Nb(4) atom.
Ba3ZrNb5O12 crystallizes in the tetragonal P4/nmm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to four equivalent O(4) and eight equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, corners with eight equivalent Ba(2)O12 cuboctahedra, faces with two equivalent Ba(2)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Zr(1)O6 octahedra, and faces with four equivalent Nb(4)O6 octahedra. All Ba(1)-O(4) bond lengths are 2.99 Å. All Ba(1)-O(5) bond lengths are 2.96 Å. In the second Ba site, Ba(2) is bonded to two equivalent O(2), two equivalent O(3), four equivalent O(1), and four equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, corners with four equivalent Ba(2)O12 cuboctahedra,  a faceface with one Ba(1)O12 cuboctahedra, faces with four equivalent Ba(2)O12 cuboctahedra, faces with two equivalent Zr(1)O6 octahedra, faces with two equivalent Nb(4)O6 octahedra, faces with two equivalent Nb(1)O5 square pyramids, and faces with two equivalent Nb(2)O5 square pyramids. Both Ba(2)-O(2) bond lengths are 3.00 Å. Both Ba(2)-O(3) bond lengths are 2.99 Å. All Ba(2)-O(1) bond lengths are 2.88 Å. All Ba(2)-O(5) bond lengths are 3.04 Å. Zr(1) is bonded to one O(3), one O(4), and four equivalent O(5) atoms to form ZrO6 octahedra that share corners with five equivalent Nb(4)O6 octahedra,  a cornercorner with one Nb(2)O5 square pyramid, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-3°. The Zr(1)-O(3) bond length is 2.05 Å. The Zr(1)-O(4) bond length is 2.16 Å. All Zr(1)-O(5) bond lengths are 2.16 Å. There are four inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2) and four equivalent O(1) atoms to form NbO5 square pyramids that share  a cornercorner with one Nb(4)O6 octahedra, corners with four equivalent Nb(2)O5 square pyramids, and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. The Nb(1)-O(2) bond length is 2.21 Å. All Nb(1)-O(1) bond lengths are 2.12 Å. In the second Nb site, Nb(2) is bonded to one O(3) and four equivalent O(1) atoms to form NbO5 square pyramids that share  a cornercorner with one Zr(1)O6 octahedra, corners with four equivalent Nb(1)O5 square pyramids, and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. The Nb(2)-O(3) bond length is 2.16 Å. All Nb(2)-O(1) bond lengths are 2.12 Å. In the third Nb site, Nb(3) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(6) atoms. Both Nb(3)-O(1) bond lengths are 2.14 Å. Both Nb(3)-O(6) bond lengths are 2.12 Å. In the fourth Nb site, Nb(4) is bonded to one O(2), one O(4), and four equivalent O(5) atoms to form NbO6 octahedra that share corners with five equivalent Zr(1)O6 octahedra,  a cornercorner with one Nb(1)O5 square pyramid, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-3°. The Nb(4)-O(2) bond length is 1.99 Å. The Nb(4)-O(4) bond length is 2.06 Å. All Nb(4)-O(5) bond lengths are 2.08 Å. There are six inequivalent O sites. In the first O site, O(5) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Zr(1), and one Nb(4) atom. In the second O site, O(6) is bonded in a square co-planar geometry to four equivalent Nb(3) atoms. In the third O site, O(1) is bonded to two equivalent Ba(2), one Nb(1), one Nb(2), and one Nb(3) atom to form a mixture of distorted edge and corner-sharing OBa2Nb3 trigonal bipyramids. In the fourth O site, O(2) is bonded in a distorted linear geometry to four equivalent Ba(2), one Nb(1), and one Nb(4) atom. In the fifth O site, O(3) is bonded in a distorted linear geometry to four equivalent Ba(2), one Zr(1), and one Nb(2) atom. In the sixth O site, O(4) is bonded in a distorted linear geometry to four equivalent Ba(1), one Zr(1), and one Nb(4) atom.