Ba4CaTi5O15 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to four equivalent O(2), four equivalent O(4), 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, corners with four equivalent Ca(1)O12 cuboctahedra,  a faceface with one Ba(2)O12 cuboctahedra,  a faceface with one Ca(1)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ti(1)O6 octahedra, and faces with four equivalent Ti(2)O6 octahedra. In the second Ba site, Ba(2) is bonded to four equivalent O(3), four equivalent O(5), and four equivalent O(6) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, corners with eight equivalent Ba(2)O12 cuboctahedra,  a faceface with one Ba(1)O12 cuboctahedra, faces with five equivalent Ba(2)O12 cuboctahedra, faces with four equivalent Ti(2)O6 octahedra, and faces with four equivalent Ti(3)O6 octahedra. Ca(1) is bonded to four equivalent O(1) and eight equivalent O(4) atoms to form CaO12 cuboctahedra that share corners with four equivalent Ca(1)O12 cuboctahedra, corners with eight equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ca(1)O12 cuboctahedra, and faces with eight equivalent Ti(1)O6 octahedra. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with five equivalent Ti(1)O6 octahedra, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Ca(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the second Ti site, Ti(2) is bonded to one O(2), one O(3), and four equivalent O(5) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra, corners with four equivalent Ti(2)O6 octahedra, 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 0-1°. In the third Ti site, Ti(3) is bonded to two equivalent O(3) and four equivalent O(6) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with four equivalent Ti(3)O6 octahedra, and faces with eight equivalent Ba(2)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 linear geometry to four equivalent Ca(1) and two equivalent Ti(1) atoms. In the second O site, O(2) is bonded to four equivalent Ba(1), one Ti(1), and one Ti(2) atom to form a mixture of distorted corner and edge-sharing OBa4Ti2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded in a distorted linear geometry to four equivalent Ba(2), one Ti(2), and one Ti(3) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ca(1), and two equivalent Ti(1) atoms. In the fifth O site, O(5) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Ti(2) atoms. In the sixth O site, O(6) is bonded in a distorted linear geometry to four equivalent Ba(2) and two equivalent Ti(3) atoms.
Ba4CaTi5O15 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to four equivalent O(2), four equivalent O(4), 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, corners with four equivalent Ca(1)O12 cuboctahedra,  a faceface with one Ba(2)O12 cuboctahedra,  a faceface with one Ca(1)O12 cuboctahedra, faces with four equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ti(1)O6 octahedra, and faces with four equivalent Ti(2)O6 octahedra. All Ba(1)-O(2) bond lengths are 2.83 Å. All Ba(1)-O(4) bond lengths are 2.91 Å. All Ba(1)-O(5) bond lengths are 2.85 Å. In the second Ba site, Ba(2) is bonded to four equivalent O(3), four equivalent O(5), and four equivalent O(6) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(1)O12 cuboctahedra, corners with eight equivalent Ba(2)O12 cuboctahedra,  a faceface with one Ba(1)O12 cuboctahedra, faces with five equivalent Ba(2)O12 cuboctahedra, faces with four equivalent Ti(2)O6 octahedra, and faces with four equivalent Ti(3)O6 octahedra. All Ba(2)-O(3) bond lengths are 2.83 Å. All Ba(2)-O(5) bond lengths are 2.84 Å. All Ba(2)-O(6) bond lengths are 2.83 Å. Ca(1) is bonded to four equivalent O(1) and eight equivalent O(4) atoms to form CaO12 cuboctahedra that share corners with four equivalent Ca(1)O12 cuboctahedra, corners with eight equivalent Ba(1)O12 cuboctahedra, faces with two equivalent Ba(1)O12 cuboctahedra, faces with four equivalent Ca(1)O12 cuboctahedra, and faces with eight equivalent Ti(1)O6 octahedra. All Ca(1)-O(1) bond lengths are 2.83 Å. All Ca(1)-O(4) bond lengths are 2.74 Å. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with five equivalent Ti(1)O6 octahedra, faces with four equivalent Ba(1)O12 cuboctahedra, and faces with four equivalent Ca(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-3°. The Ti(1)-O(1) bond length is 1.92 Å. The Ti(1)-O(2) bond length is 2.05 Å. All Ti(1)-O(4) bond lengths are 2.01 Å. In the second Ti site, Ti(2) is bonded to one O(2), one O(3), and four equivalent O(5) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra, corners with four equivalent Ti(2)O6 octahedra, 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 0-1°. The Ti(2)-O(2) bond length is 2.02 Å. The Ti(2)-O(3) bond length is 2.02 Å. All Ti(2)-O(5) bond lengths are 2.00 Å. In the third Ti site, Ti(3) is bonded to two equivalent O(3) and four equivalent O(6) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with four equivalent Ti(3)O6 octahedra, and faces with eight equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Ti(3)-O(3) bond lengths are 2.01 Å. All Ti(3)-O(6) bond lengths are 2.00 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to four equivalent Ca(1) and two equivalent Ti(1) atoms. In the second O site, O(2) is bonded to four equivalent Ba(1), one Ti(1), and one Ti(2) atom to form a mixture of distorted corner and edge-sharing OBa4Ti2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded in a distorted linear geometry to four equivalent Ba(2), one Ti(2), and one Ti(3) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ca(1), and two equivalent Ti(1) atoms. In the fifth O site, O(5) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Ti(2) atoms. In the sixth O site, O(6) is bonded in a distorted linear geometry to four equivalent Ba(2) and two equivalent Ti(3) atoms.