Ba5Ta2O9Cl2 crystallizes in the hexagonal P6_3/mmc space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 7-coordinate geometry to three equivalent O(1) and four equivalent Cl(1) atoms. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to three equivalent O(2), six equivalent O(1), and one Cl(1) atom. In the third Ba site, Ba(3) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(3)O12 cuboctahedra and faces with six equivalent Ta(1)O6 octahedra. Ta(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted TaO6 octahedra that share faces with three equivalent Ba(3)O12 cuboctahedra and  a faceface with one Ta(1)O6 octahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(3), two equivalent Ba(2), and one Ta(1) atom. In the second O site, O(2) is bonded to two equivalent Ba(2), two equivalent Ba(3), and two equivalent Ta(1) atoms to form distorted OBa4Ta2 octahedra that share corners with six equivalent O(2)Ba4Ta2 octahedra, corners with two equivalent Cl(1)Ba5 trigonal bipyramids, and faces with four equivalent O(2)Ba4Ta2 octahedra. The corner-sharing octahedral tilt angles range from 7-60°. Cl(1) is bonded to one Ba(2) and four equivalent Ba(1) atoms to form distorted ClBa5 trigonal bipyramids that share corners with three equivalent O(2)Ba4Ta2 octahedra, corners with six equivalent Cl(1)Ba5 trigonal bipyramids, and edges with three equivalent Cl(1)Ba5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 45°.
Ba5Ta2O9Cl2 crystallizes in the hexagonal P6_3/mmc space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 7-coordinate geometry to three equivalent O(1) and four equivalent Cl(1) atoms. All Ba(1)-O(1) bond lengths are 2.57 Å. There is one shorter (3.22 Å) and three longer (3.60 Å) Ba(1)-Cl(1) bond lengths. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to three equivalent O(2), six equivalent O(1), and one Cl(1) atom. All Ba(2)-O(2) bond lengths are 2.76 Å. All Ba(2)-O(1) bond lengths are 3.05 Å. The Ba(2)-Cl(1) bond length is 3.15 Å. In the third Ba site, Ba(3) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(3)O12 cuboctahedra and faces with six equivalent Ta(1)O6 octahedra. All Ba(3)-O(1) bond lengths are 2.98 Å. All Ba(3)-O(2) bond lengths are 3.03 Å. Ta(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted TaO6 octahedra that share faces with three equivalent Ba(3)O12 cuboctahedra and  a faceface with one Ta(1)O6 octahedra. All Ta(1)-O(1) bond lengths are 1.90 Å. All Ta(1)-O(2) bond lengths are 2.17 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Ba(1), one Ba(3), two equivalent Ba(2), and one Ta(1) atom. In the second O site, O(2) is bonded to two equivalent Ba(2), two equivalent Ba(3), and two equivalent Ta(1) atoms to form distorted OBa4Ta2 octahedra that share corners with six equivalent O(2)Ba4Ta2 octahedra, corners with two equivalent Cl(1)Ba5 trigonal bipyramids, and faces with four equivalent O(2)Ba4Ta2 octahedra. The corner-sharing octahedral tilt angles range from 7-60°. Cl(1) is bonded to one Ba(2) and four equivalent Ba(1) atoms to form distorted ClBa5 trigonal bipyramids that share corners with three equivalent O(2)Ba4Ta2 octahedra, corners with six equivalent Cl(1)Ba5 trigonal bipyramids, and edges with three equivalent Cl(1)Ba5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 45°.