YBa2Cu4O8 crystallizes in the orthorhombic Cmmm space group. Ba(1) is bonded in a 8-coordinate geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. Y(1) is bonded in a linear geometry to two equivalent O(3) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form corner-sharing CuO5 trigonal bipyramids. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to one O(1) and three equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) 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(1)Ba4Cu2 octahedra, corners with four equivalent O(3)Ba2YCu2 trigonal bipyramids, edges with four equivalent O(1)Ba4Cu2 octahedra, and faces with two equivalent O(3)Ba2YCu2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Cu(1) atoms. In the third O site, O(3) is bonded to two equivalent Ba(1), one Y(1), and two equivalent Cu(1) atoms to form OBa2YCu2 trigonal bipyramids that share corners with four equivalent O(1)Ba4Cu2 octahedra, corners with five equivalent O(3)Ba2YCu2 trigonal bipyramids, and faces with two equivalent O(1)Ba4Cu2 octahedra. The corner-sharing octahedral tilt angles are 57°. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to two equivalent Ba(1) and three equivalent Cu(2) atoms.
YBa2Cu4O8 crystallizes in the orthorhombic Cmmm space group. Ba(1) is bonded in a 8-coordinate geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. Both Ba(1)-O(3) bond lengths are 2.69 Å. Both Ba(1)-O(4) bond lengths are 3.05 Å. All Ba(1)-O(1) bond lengths are 2.74 Å. Y(1) is bonded in a linear geometry to two equivalent O(3) atoms. Both Y(1)-O(3) bond lengths are 2.18 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form corner-sharing CuO5 trigonal bipyramids. The Cu(1)-O(1) bond length is 2.16 Å. Both Cu(1)-O(2) bond lengths are 2.07 Å. Both Cu(1)-O(3) bond lengths are 1.99 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to one O(1) and three equivalent O(4) atoms. The Cu(2)-O(1) bond length is 1.87 Å. There are two shorter (1.89 Å) and one longer (1.91 Å) Cu(2)-O(4) bond length. There are four inequivalent O sites. In the first O site, O(1) 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(1)Ba4Cu2 octahedra, corners with four equivalent O(3)Ba2YCu2 trigonal bipyramids, edges with four equivalent O(1)Ba4Cu2 octahedra, and faces with two equivalent O(3)Ba2YCu2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Cu(1) atoms. In the third O site, O(3) is bonded to two equivalent Ba(1), one Y(1), and two equivalent Cu(1) atoms to form OBa2YCu2 trigonal bipyramids that share corners with four equivalent O(1)Ba4Cu2 octahedra, corners with five equivalent O(3)Ba2YCu2 trigonal bipyramids, and faces with two equivalent O(1)Ba4Cu2 octahedra. The corner-sharing octahedral tilt angles are 57°. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to two equivalent Ba(1) and three equivalent Cu(2) atoms.