Ba8Ca3Nb5O24 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal I4/mmm space group. Ba(1) is bonded to one O(4), one O(6), two equivalent O(2), two equivalent O(3), two equivalent O(5), and four equivalent O(1) atoms to form BaO12 cuboctahedra that share corners with twelve equivalent Ba(1)O12 cuboctahedra, faces with six equivalent Ba(1)O12 cuboctahedra,  a faceface with one Ca(2)O6 octahedra,  a faceface with one Nb(3)O6 octahedra, faces with two equivalent Ca(1)O6 octahedra, faces with two equivalent Nb(1)O6 octahedra, and faces with two equivalent Nb(2)O6 octahedra. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent O(5) and four equivalent O(1) atoms to form CaO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-10°. In the second Ca site, Ca(2) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form CaO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. In the third Ca site, Ca(2) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form CaO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(4), one O(6), and four equivalent O(1) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Ca(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra, corners with four equivalent Ca(1)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-10°. In the second Nb site, Nb(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form NbO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra, corners with two equivalent Ca(2)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. In the third Nb site, Nb(3) is bonded to two equivalent O(6) and four equivalent O(3) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to four equivalent Ba(1), one Ca(1), and one Nb(1) atom. In the second O site, O(2) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ca(2), and one Nb(2) atom. In the third O site, O(3) is bonded in a distorted linear geometry to four equivalent Ba(1), one Nb(2), and one Nb(3) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ca(2), and one Nb(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 Nb(2) atom. In the sixth O site, O(6) is bonded to four equivalent Ba(1), one Nb(1), and one Nb(3) atom to form distorted corner-sharing OBa4Nb2 octahedra. The corner-sharing octahedra are not tilted.
Ba8Ca3Nb5O24 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal I4/mmm space group. Ba(1) is bonded to one O(4), one O(6), two equivalent O(2), two equivalent O(3), two equivalent O(5), and four equivalent O(1) atoms to form BaO12 cuboctahedra that share corners with twelve equivalent Ba(1)O12 cuboctahedra, faces with six equivalent Ba(1)O12 cuboctahedra,  a faceface with one Ca(2)O6 octahedra,  a faceface with one Nb(3)O6 octahedra, faces with two equivalent Ca(1)O6 octahedra, faces with two equivalent Nb(1)O6 octahedra, and faces with two equivalent Nb(2)O6 octahedra. The Ba(1)-O(4) bond length is 3.05 Å. The Ba(1)-O(6) bond length is 2.96 Å. Both Ba(1)-O(2) bond lengths are 3.05 Å. Both Ba(1)-O(3) bond lengths are 3.00 Å. Both Ba(1)-O(5) bond lengths are 3.01 Å. There are two shorter (2.90 Å) and two longer (3.16 Å) Ba(1)-O(1) bond lengths. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent O(5) and four equivalent O(1) atoms to form CaO6 octahedra that share corners with two equivalent Nb(2)O6 octahedra, corners with four equivalent Nb(1)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-10°. Both Ca(1)-O(5) bond lengths are 2.32 Å. All Ca(1)-O(1) bond lengths are 2.28 Å. In the second Ca site, Ca(2) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form CaO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Ca(2)-O(4) bond lengths are 2.31 Å. All Ca(2)-O(2) bond lengths are 2.28 Å. In the third Ca site, Ca(2) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form CaO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Ca(2)-O(4) bond lengths are 2.31 Å. All Ca(2)-O(2) bond lengths are 2.28 Å. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(4), one O(6), and four equivalent O(1) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Ca(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra, corners with four equivalent Ca(1)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-10°. The Nb(1)-O(4) bond length is 1.91 Å. The Nb(1)-O(6) bond length is 2.42 Å. All Nb(1)-O(1) bond lengths are 1.99 Å. In the second Nb site, Nb(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms to form NbO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra, corners with two equivalent Ca(2)O6 octahedra, corners with two equivalent Nb(3)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Nb(2)-O(2) bond lengths are 1.97 Å. Both Nb(2)-O(3) bond lengths are 2.17 Å. Both Nb(2)-O(5) bond lengths are 1.99 Å. In the third Nb site, Nb(3) is bonded to two equivalent O(6) and four equivalent O(3) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with eight equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Nb(3)-O(6) bond lengths are 1.99 Å. All Nb(3)-O(3) bond lengths are 2.08 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to four equivalent Ba(1), one Ca(1), and one Nb(1) atom. In the second O site, O(2) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ca(2), and one Nb(2) atom. In the third O site, O(3) is bonded in a distorted linear geometry to four equivalent Ba(1), one Nb(2), and one Nb(3) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to four equivalent Ba(1), one Ca(2), and one Nb(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 Nb(2) atom. In the sixth O site, O(6) is bonded to four equivalent Ba(1), one Nb(1), and one Nb(3) atom to form distorted corner-sharing OBa4Nb2 octahedra. The corner-sharing octahedra are not tilted.