YCu3Mn4O12 crystallizes in the orthorhombic Pmmm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to four equivalent O(2), four equivalent O(3), and four equivalent O(5) atoms to form YO12 cuboctahedra that share faces with eight equivalent Mn(1)O6 octahedra. In the second Y site, Y(2) is bonded to four equivalent O(1), four equivalent O(4), and four equivalent O(6) atoms to form YO12 cuboctahedra that share faces with eight equivalent Mn(1)O6 octahedra. Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form MnO6 octahedra that share corners with six equivalent Mn(1)O6 octahedra,  a faceface with one Y(1)O12 cuboctahedra, and  a faceface with one Y(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 41-43°. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to four equivalent O(6) atoms. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to four equivalent O(3) atoms. In the third Cu site, Cu(3) is bonded in a square co-planar geometry to four equivalent O(2) atoms. In the fourth Cu site, Cu(4) is bonded in a square co-planar geometry to four equivalent O(5) atoms. In the fifth Cu site, Cu(5) is bonded in a square co-planar geometry to four equivalent O(4) atoms. In the sixth Cu site, Cu(6) is bonded in a square co-planar geometry to four equivalent O(1) atoms. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Y(2), two equivalent Mn(1), and one Cu(6) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Y(1), two equivalent Mn(1), and one Cu(3) atom. In the third O site, O(3) is bonded to one Y(1), two equivalent Mn(1), and one Cu(2) atom to form a mixture of distorted corner and edge-sharing OYMn2Cu tetrahedra. In the fourth O site, O(4) is bonded to one Y(2), two equivalent Mn(1), and one Cu(5) atom to form a mixture of distorted corner and edge-sharing OYMn2Cu tetrahedra. In the fifth O site, O(5) is bonded to one Y(1), two equivalent Mn(1), and one Cu(4) atom to form a mixture of distorted corner and edge-sharing OYMn2Cu tetrahedra. In the sixth O site, O(6) is bonded to one Y(2), two equivalent Mn(1), and one Cu(1) atom to form a mixture of distorted corner and edge-sharing OYMn2Cu tetrahedra.
YCu3Mn4O12 crystallizes in the orthorhombic Pmmm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to four equivalent O(2), four equivalent O(3), and four equivalent O(5) atoms to form YO12 cuboctahedra that share faces with eight equivalent Mn(1)O6 octahedra. All Y(1)-O(2) bond lengths are 2.61 Å. All Y(1)-O(3) bond lengths are 2.56 Å. All Y(1)-O(5) bond lengths are 2.55 Å. In the second Y site, Y(2) is bonded to four equivalent O(1), four equivalent O(4), and four equivalent O(6) atoms to form YO12 cuboctahedra that share faces with eight equivalent Mn(1)O6 octahedra. All Y(2)-O(1) bond lengths are 2.60 Å. All Y(2)-O(4) bond lengths are 2.58 Å. All Y(2)-O(6) bond lengths are 2.54 Å. Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form MnO6 octahedra that share corners with six equivalent Mn(1)O6 octahedra,  a faceface with one Y(1)O12 cuboctahedra, and  a faceface with one Y(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 41-43°. The Mn(1)-O(1) bond length is 2.00 Å. The Mn(1)-O(2) bond length is 2.00 Å. The Mn(1)-O(3) bond length is 1.95 Å. The Mn(1)-O(4) bond length is 1.97 Å. The Mn(1)-O(5) bond length is 2.00 Å. The Mn(1)-O(6) bond length is 2.00 Å. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to four equivalent O(6) atoms. All Cu(1)-O(6) bond lengths are 1.91 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to four equivalent O(3) atoms. All Cu(2)-O(3) bond lengths are 1.99 Å. In the third Cu site, Cu(3) is bonded in a square co-planar geometry to four equivalent O(2) atoms. All Cu(3)-O(2) bond lengths are 1.91 Å. In the fourth Cu site, Cu(4) is bonded in a square co-planar geometry to four equivalent O(5) atoms. All Cu(4)-O(5) bond lengths are 1.91 Å. In the fifth Cu site, Cu(5) is bonded in a square co-planar geometry to four equivalent O(4) atoms. All Cu(5)-O(4) bond lengths are 1.96 Å. In the sixth Cu site, Cu(6) is bonded in a square co-planar geometry to four equivalent O(1) atoms. All Cu(6)-O(1) bond lengths are 1.91 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Y(2), two equivalent Mn(1), and one Cu(6) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Y(1), two equivalent Mn(1), and one Cu(3) atom. In the third O site, O(3) is bonded to one Y(1), two equivalent Mn(1), and one Cu(2) atom to form a mixture of distorted corner and edge-sharing OYMn2Cu tetrahedra. In the fourth O site, O(4) is bonded to one Y(2), two equivalent Mn(1), and one Cu(5) atom to form a mixture of distorted corner and edge-sharing OYMn2Cu tetrahedra. In the fifth O site, O(5) is bonded to one Y(1), two equivalent Mn(1), and one Cu(4) atom to form a mixture of distorted corner and edge-sharing OYMn2Cu tetrahedra. In the sixth O site, O(6) is bonded to one Y(2), two equivalent Mn(1), and one Cu(1) atom to form a mixture of distorted corner and edge-sharing OYMn2Cu tetrahedra.