Ba3ZrTa4O15 crystallizes in the tetragonal P4bm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. In the second Ba site, Ba(2) is bonded to four equivalent O(2) and eight equivalent O(5) atoms to form BaO12 cuboctahedra that share faces with two equivalent Ba(2)O12 cuboctahedra and faces with eight equivalent Ta(1)O6 octahedra. Zr(1) is bonded to two equivalent O(4) and four equivalent O(3) atoms to form ZrO6 octahedra that share corners with two equivalent Zr(1)O6 octahedra and corners with four equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-39°. Ta(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(5) atoms to form TaO6 octahedra that share  a cornercorner with one Zr(1)O6 octahedra, corners with five equivalent Ta(1)O6 octahedra, and faces with two equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 7-39°. There are five inequivalent O sites. In the first O site, O(4) is bonded in a linear geometry to two equivalent Ba(1) and two equivalent Zr(1) atoms. In the second O site, O(5) is bonded in a distorted linear geometry to two equivalent Ba(2) and two equivalent Ta(1) atoms. In the third O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1) and two equivalent Ta(1) atoms. In the fourth O site, O(2) is bonded in a distorted linear geometry to one Ba(1), one Ba(2), and two equivalent Ta(1) atoms. In the fifth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(1), one Zr(1), and one Ta(1) atom.
Ba3ZrTa4O15 crystallizes in the tetragonal P4bm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. The Ba(1)-O(4) bond length is 3.07 Å. There is one shorter (2.87 Å) and one longer (2.94 Å) Ba(1)-O(1) bond length. Both Ba(1)-O(2) bond lengths are 3.25 Å. There are two shorter (2.83 Å) and two longer (2.93 Å) Ba(1)-O(3) bond lengths. In the second Ba site, Ba(2) is bonded to four equivalent O(2) and eight equivalent O(5) atoms to form BaO12 cuboctahedra that share faces with two equivalent Ba(2)O12 cuboctahedra and faces with eight equivalent Ta(1)O6 octahedra. All Ba(2)-O(2) bond lengths are 2.82 Å. There are four shorter (2.79 Å) and four longer (2.86 Å) Ba(2)-O(5) bond lengths. Zr(1) is bonded to two equivalent O(4) and four equivalent O(3) atoms to form ZrO6 octahedra that share corners with two equivalent Zr(1)O6 octahedra and corners with four equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-39°. Both Zr(1)-O(4) bond lengths are 2.03 Å. All Zr(1)-O(3) bond lengths are 2.12 Å. Ta(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(5) atoms to form TaO6 octahedra that share  a cornercorner with one Zr(1)O6 octahedra, corners with five equivalent Ta(1)O6 octahedra, and faces with two equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 7-39°. The Ta(1)-O(1) bond length is 2.03 Å. The Ta(1)-O(3) bond length is 1.92 Å. There is one shorter (1.94 Å) and one longer (2.13 Å) Ta(1)-O(2) bond length. There is one shorter (2.05 Å) and one longer (2.06 Å) Ta(1)-O(5) bond length. There are five inequivalent O sites. In the first O site, O(4) is bonded in a linear geometry to two equivalent Ba(1) and two equivalent Zr(1) atoms. In the second O site, O(5) is bonded in a distorted linear geometry to two equivalent Ba(2) and two equivalent Ta(1) atoms. In the third O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1) and two equivalent Ta(1) atoms. In the fourth O site, O(2) is bonded in a distorted linear geometry to one Ba(1), one Ba(2), and two equivalent Ta(1) atoms. In the fifth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ba(1), one Zr(1), and one Ta(1) atom.