YbBa2Cu4O8 crystallizes in the orthorhombic Cmmm space group. Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and four equivalent O(4) atoms. Yb(1) is bonded in a body-centered cubic geometry to four equivalent O(2) and four equivalent O(3) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(4), two equivalent O(2), and two equivalent O(3) atoms to form distorted corner-sharing CuO5 square pyramids. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to one O(4) and three equivalent O(1) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to two equivalent Ba(1) and three equivalent Cu(2) atoms. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Yb(1), and two equivalent Cu(1) atoms to form distorted OBa2Yb2Cu2 octahedra that share corners with four equivalent O(2)Ba2Yb2Cu2 octahedra, corners with four equivalent O(3)Ba2Yb2Cu2 octahedra, corners with four equivalent O(4)Ba4Cu2 octahedra, edges with three equivalent O(2)Ba2Yb2Cu2 octahedra, faces with two equivalent O(4)Ba4Cu2 octahedra, and faces with four equivalent O(3)Ba2Yb2Cu2 octahedra. The corner-sharing octahedral tilt angles range from 0-68°. In the third O site, O(3) is bonded to two equivalent Ba(1), two equivalent Yb(1), and two equivalent Cu(1) atoms to form distorted OBa2Yb2Cu2 octahedra that share corners with four equivalent O(2)Ba2Yb2Cu2 octahedra, corners with four equivalent O(3)Ba2Yb2Cu2 octahedra, corners with four equivalent O(4)Ba4Cu2 octahedra, edges with three equivalent O(3)Ba2Yb2Cu2 octahedra, faces with two equivalent O(4)Ba4Cu2 octahedra, and faces with four equivalent O(2)Ba2Yb2Cu2 octahedra. The corner-sharing octahedral tilt angles range from 0-68°. In the fourth O site, O(4) is bonded to four equivalent Ba(1), one Cu(1), and one Cu(2) atom to form distorted OBa4Cu2 octahedra that share corners with four equivalent O(2)Ba2Yb2Cu2 octahedra, corners with four equivalent O(3)Ba2Yb2Cu2 octahedra, corners with four equivalent O(4)Ba4Cu2 octahedra, edges with four equivalent O(4)Ba4Cu2 octahedra, faces with two equivalent O(2)Ba2Yb2Cu2 octahedra, and faces with two equivalent O(3)Ba2Yb2Cu2 octahedra. The corner-sharing octahedral tilt angles range from 19-54°.
YbBa2Cu4O8 crystallizes in the orthorhombic Cmmm space group. Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and four equivalent O(4) atoms. Both Ba(1)-O(1) bond lengths are 3.16 Å. Both Ba(1)-O(2) bond lengths are 2.90 Å. Both Ba(1)-O(3) bond lengths are 2.88 Å. All Ba(1)-O(4) bond lengths are 2.76 Å. Yb(1) is bonded in a body-centered cubic geometry to four equivalent O(2) and four equivalent O(3) atoms. All Yb(1)-O(2) bond lengths are 2.43 Å. All Yb(1)-O(3) bond lengths are 2.43 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(4), two equivalent O(2), and two equivalent O(3) atoms to form distorted corner-sharing CuO5 square pyramids. The Cu(1)-O(4) bond length is 2.50 Å. Both Cu(1)-O(2) bond lengths are 1.92 Å. Both Cu(1)-O(3) bond lengths are 1.93 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to one O(4) and three equivalent O(1) atoms. The Cu(2)-O(4) bond length is 1.83 Å. There is one shorter (1.89 Å) and two longer (1.93 Å) Cu(2)-O(1) bond lengths. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to two equivalent Ba(1) and three equivalent Cu(2) atoms. In the second O site, O(2) is bonded to two equivalent Ba(1), two equivalent Yb(1), and two equivalent Cu(1) atoms to form distorted OBa2Yb2Cu2 octahedra that share corners with four equivalent O(2)Ba2Yb2Cu2 octahedra, corners with four equivalent O(3)Ba2Yb2Cu2 octahedra, corners with four equivalent O(4)Ba4Cu2 octahedra, edges with three equivalent O(2)Ba2Yb2Cu2 octahedra, faces with two equivalent O(4)Ba4Cu2 octahedra, and faces with four equivalent O(3)Ba2Yb2Cu2 octahedra. The corner-sharing octahedral tilt angles range from 0-68°. In the third O site, O(3) is bonded to two equivalent Ba(1), two equivalent Yb(1), and two equivalent Cu(1) atoms to form distorted OBa2Yb2Cu2 octahedra that share corners with four equivalent O(2)Ba2Yb2Cu2 octahedra, corners with four equivalent O(3)Ba2Yb2Cu2 octahedra, corners with four equivalent O(4)Ba4Cu2 octahedra, edges with three equivalent O(3)Ba2Yb2Cu2 octahedra, faces with two equivalent O(4)Ba4Cu2 octahedra, and faces with four equivalent O(2)Ba2Yb2Cu2 octahedra. The corner-sharing octahedral tilt angles range from 0-68°. In the fourth O site, O(4) is bonded to four equivalent Ba(1), one Cu(1), and one Cu(2) atom to form distorted OBa4Cu2 octahedra that share corners with four equivalent O(2)Ba2Yb2Cu2 octahedra, corners with four equivalent O(3)Ba2Yb2Cu2 octahedra, corners with four equivalent O(4)Ba4Cu2 octahedra, edges with four equivalent O(4)Ba4Cu2 octahedra, faces with two equivalent O(2)Ba2Yb2Cu2 octahedra, and faces with two equivalent O(3)Ba2Yb2Cu2 octahedra. The corner-sharing octahedral tilt angles range from 19-54°.