Ba5Ca2Ta3O15 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal I4/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(1), one O(2), one O(7), two equivalent O(3), two equivalent O(4), two equivalent O(5), and three equivalent O(6) atoms to form BaO12 cuboctahedra that share corners with three equivalent Ba(2)O12 cuboctahedra, corners with nine equivalent Ba(1)O12 cuboctahedra,  a faceface with one Ba(2)O12 cuboctahedra, faces with five equivalent Ba(1)O12 cuboctahedra,  a faceface with one Ta(2)O6 octahedra,  a faceface with one Ta(3)O6 octahedra, faces with three equivalent Ca(1)O6 octahedra, and faces with three equivalent Ta(1)O6 octahedra. In the second Ba site, Ba(2) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(6) atoms to form BaO12 cuboctahedra that share corners with twelve equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Ba(2)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ca(1)O6 octahedra, and faces with four equivalent Ta(1)O6 octahedra. Ca(1) is bonded to one O(1), one O(2), one O(4), one O(5), and two equivalent O(6) atoms to form CaO6 octahedra that share  a cornercorner with one Ta(2)O6 octahedra, corners with five equivalent Ta(1)O6 octahedra, faces with two equivalent Ba(2)O12 cuboctahedra, and faces with six equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-7°. There are three inequivalent Ta sites. In the first Ta site, Ta(3) is bonded to two equivalent O(7) and four equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(2)O6 octahedra, corners with four equivalent Ta(1)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. In the second Ta site, Ta(1) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(6) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(3)O6 octahedra, corners with five equivalent Ca(1)O6 octahedra, faces with two equivalent Ba(2)O12 cuboctahedra, and faces with six equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the third Ta site, Ta(2) is bonded to two equivalent O(7) and four equivalent O(5) atoms to form TaO6 octahedra that share corners with two equivalent Ta(3)O6 octahedra, corners with four equivalent Ca(1)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Ca(1), and one Ta(1) atom. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Ca(1), and one Ta(1) atom. In the third O site, O(3) is bonded to four equivalent Ba(1), one Ta(1), and one Ta(3) atom to form a mixture of distorted corner and face-sharing OBa4Ta2 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ca(1), and one Ta(1) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ca(1), and one Ta(2) atom. In the sixth O site, O(6) is bonded in a distorted linear geometry to one Ba(2), three equivalent Ba(1), one Ca(1), and one Ta(1) atom. In the seventh O site, O(7) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ta(2), and one Ta(3) atom.
Ba5Ca2Ta3O15 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal I4/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(1), one O(2), one O(7), two equivalent O(3), two equivalent O(4), two equivalent O(5), and three equivalent O(6) atoms to form BaO12 cuboctahedra that share corners with three equivalent Ba(2)O12 cuboctahedra, corners with nine equivalent Ba(1)O12 cuboctahedra,  a faceface with one Ba(2)O12 cuboctahedra, faces with five equivalent Ba(1)O12 cuboctahedra,  a faceface with one Ta(2)O6 octahedra,  a faceface with one Ta(3)O6 octahedra, faces with three equivalent Ca(1)O6 octahedra, and faces with three equivalent Ta(1)O6 octahedra. The Ba(1)-O(1) bond length is 2.94 Å. The Ba(1)-O(2) bond length is 3.06 Å. The Ba(1)-O(7) bond length is 3.01 Å. Both Ba(1)-O(3) bond lengths are 2.99 Å. There is one shorter (2.93 Å) and one longer (3.11 Å) Ba(1)-O(4) bond length. There is one shorter (3.03 Å) and one longer (3.04 Å) Ba(1)-O(5) bond length. There are two shorter (2.95 Å) and one longer (3.12 Å) Ba(1)-O(6) bond length. In the second Ba site, Ba(2) is bonded to four equivalent O(1), four equivalent O(2), and four equivalent O(6) atoms to form BaO12 cuboctahedra that share corners with twelve equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Ba(2)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ca(1)O6 octahedra, and faces with four equivalent Ta(1)O6 octahedra. All Ba(2)-O(1) bond lengths are 3.08 Å. All Ba(2)-O(2) bond lengths are 3.00 Å. All Ba(2)-O(6) bond lengths are 3.11 Å. Ca(1) is bonded to one O(1), one O(2), one O(4), one O(5), and two equivalent O(6) atoms to form CaO6 octahedra that share  a cornercorner with one Ta(2)O6 octahedra, corners with five equivalent Ta(1)O6 octahedra, faces with two equivalent Ba(2)O12 cuboctahedra, and faces with six equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-7°. The Ca(1)-O(1) bond length is 2.30 Å. The Ca(1)-O(2) bond length is 2.33 Å. The Ca(1)-O(4) bond length is 2.29 Å. The Ca(1)-O(5) bond length is 2.29 Å. Both Ca(1)-O(6) bond lengths are 2.27 Å. There are three inequivalent Ta sites. In the first Ta site, Ta(3) is bonded to two equivalent O(7) and four equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(2)O6 octahedra, corners with four equivalent Ta(1)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Ta(3)-O(7) bond lengths are 2.09 Å. All Ta(3)-O(3) bond lengths are 2.01 Å. In the second Ta site, Ta(1) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(6) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(3)O6 octahedra, corners with five equivalent Ca(1)O6 octahedra, faces with two equivalent Ba(2)O12 cuboctahedra, and faces with six equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-7°. The Ta(1)-O(1) bond length is 1.99 Å. The Ta(1)-O(2) bond length is 1.92 Å. The Ta(1)-O(3) bond length is 2.31 Å. The Ta(1)-O(4) bond length is 1.98 Å. Both Ta(1)-O(6) bond lengths are 1.98 Å. In the third Ta site, Ta(2) is bonded to two equivalent O(7) and four equivalent O(5) atoms to form TaO6 octahedra that share corners with two equivalent Ta(3)O6 octahedra, corners with four equivalent Ca(1)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Ta(2)-O(7) bond lengths are 2.15 Å. All Ta(2)-O(5) bond lengths are 1.97 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Ca(1), and one Ta(1) atom. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Ca(1), and one Ta(1) atom. In the third O site, O(3) is bonded to four equivalent Ba(1), one Ta(1), and one Ta(3) atom to form a mixture of distorted corner and face-sharing OBa4Ta2 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ca(1), and one Ta(1) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ca(1), and one Ta(2) atom. In the sixth O site, O(6) is bonded in a distorted linear geometry to one Ba(2), three equivalent Ba(1), one Ca(1), and one Ta(1) atom. In the seventh O site, O(7) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ta(2), and one Ta(3) atom.