Ba8Bi10O27 crystallizes in the trigonal R-3 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 11-coordinate geometry to one O(5), two equivalent O(2), two equivalent O(3), three equivalent O(1), and three equivalent O(4) atoms. In the second Ba site, Ba(2) is bonded to three equivalent O(1), three equivalent O(3), three equivalent O(4), and three equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with three equivalent Ba(2)O12 cuboctahedra,  a faceface with one Bi(1)O6 octahedra,  a faceface with one Bi(3)O6 octahedra, and faces with six equivalent Bi(2)O6 octahedra. There are four inequivalent Bi sites. In the first Bi site, Bi(4) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. In the second Bi site, Bi(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form BiO6 octahedra that share corners with six equivalent Bi(2)O6 octahedra and  a faceface with one Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-13°. In the third Bi site, Bi(2) is bonded to one O(1), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form BiO6 octahedra that share  a cornercorner with one Bi(3)O6 octahedra, corners with two equivalent Bi(1)O6 octahedra, corners with three equivalent Bi(2)O6 octahedra, and faces with two equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-13°. In the fourth Bi site, Bi(3) is bonded to six equivalent O(4) atoms to form BiO6 octahedra that share corners with six equivalent Bi(2)O6 octahedra and faces with two equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 7°. There are five inequivalent O sites. In the first O site, O(5) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Bi(2) atoms to form distorted corner-sharing OBa4Bi2 octahedra. The corner-sharing octahedral tilt angles are 60°. In the second O site, O(4) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one Bi(2), and one Bi(3) atom. In the third O site, O(1) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one Bi(1), and one Bi(2) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Bi(1), one Bi(2), and one Bi(4) atom. In the fifth O site, O(3) is bonded in a 2-coordinate geometry to one Ba(2), two equivalent Ba(1), and two equivalent Bi(2) atoms.
Ba8Bi10O27 crystallizes in the trigonal R-3 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 11-coordinate geometry to one O(5), two equivalent O(2), two equivalent O(3), three equivalent O(1), and three equivalent O(4) atoms. The Ba(1)-O(5) bond length is 3.12 Å. There is one shorter (2.97 Å) and one longer (3.09 Å) Ba(1)-O(2) bond length. There is one shorter (3.00 Å) and one longer (3.03 Å) Ba(1)-O(3) bond length. There are a spread of Ba(1)-O(1) bond distances ranging from 3.07-3.35 Å. There are a spread of Ba(1)-O(4) bond distances ranging from 2.96-3.35 Å. In the second Ba site, Ba(2) is bonded to three equivalent O(1), three equivalent O(3), three equivalent O(4), and three equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with three equivalent Ba(2)O12 cuboctahedra,  a faceface with one Bi(1)O6 octahedra,  a faceface with one Bi(3)O6 octahedra, and faces with six equivalent Bi(2)O6 octahedra. All Ba(2)-O(1) bond lengths are 3.23 Å. All Ba(2)-O(3) bond lengths are 3.26 Å. All Ba(2)-O(4) bond lengths are 3.07 Å. All Ba(2)-O(5) bond lengths are 3.13 Å. There are four inequivalent Bi sites. In the first Bi site, Bi(4) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. All Bi(4)-O(2) bond lengths are 2.87 Å. In the second Bi site, Bi(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form BiO6 octahedra that share corners with six equivalent Bi(2)O6 octahedra and  a faceface with one Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-13°. All Bi(1)-O(1) bond lengths are 2.24 Å. All Bi(1)-O(2) bond lengths are 2.24 Å. In the third Bi site, Bi(2) is bonded to one O(1), one O(2), one O(4), one O(5), and two equivalent O(3) atoms to form BiO6 octahedra that share  a cornercorner with one Bi(3)O6 octahedra, corners with two equivalent Bi(1)O6 octahedra, corners with three equivalent Bi(2)O6 octahedra, and faces with two equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-13°. The Bi(2)-O(1) bond length is 2.20 Å. The Bi(2)-O(2) bond length is 2.19 Å. The Bi(2)-O(4) bond length is 2.21 Å. The Bi(2)-O(5) bond length is 2.23 Å. There is one shorter (2.21 Å) and one longer (2.22 Å) Bi(2)-O(3) bond length. In the fourth Bi site, Bi(3) is bonded to six equivalent O(4) atoms to form BiO6 octahedra that share corners with six equivalent Bi(2)O6 octahedra and faces with two equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 7°. All Bi(3)-O(4) bond lengths are 2.23 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Bi(2) atoms to form distorted corner-sharing OBa4Bi2 octahedra. The corner-sharing octahedral tilt angles are 60°. In the second O site, O(4) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one Bi(2), and one Bi(3) atom. In the third O site, O(1) is bonded in a 6-coordinate geometry to one Ba(2), three equivalent Ba(1), one Bi(1), and one Bi(2) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to two equivalent Ba(1), one Bi(1), one Bi(2), and one Bi(4) atom. In the fifth O site, O(3) is bonded in a 2-coordinate geometry to one Ba(2), two equivalent Ba(1), and two equivalent Bi(2) atoms.