Sm4ZrO8 crystallizes in the orthorhombic Immm space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. In the second Sm site, Sm(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing SmO6 octahedra. The corner-sharing octahedral tilt angles are 55°. Zr(1) is bonded in a body-centered cubic geometry to four equivalent O(3) and four equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sm(1) and two equivalent Sm(2) atoms to form OSm4 tetrahedra that share corners with two equivalent O(3)Sm2Zr2 tetrahedra, corners with four equivalent O(4)Sm2Zr2 tetrahedra, corners with four equivalent O(1)Sm4 tetrahedra, corners with six equivalent O(2)Sm4 tetrahedra,  an edgeedge with one O(3)Sm2Zr2 tetrahedra, and  an edgeedge with one O(2)Sm4 tetrahedra. In the second O site, O(2) is bonded to four equivalent Sm(2) atoms to form a mixture of corner and edge-sharing OSm4 tetrahedra. In the third O site, O(3) is bonded to two equivalent Sm(1) and two equivalent Zr(1) atoms to form OSm2Zr2 tetrahedra that share corners with two equivalent O(1)Sm4 tetrahedra, corners with four equivalent O(4)Sm2Zr2 tetrahedra, corners with six equivalent O(3)Sm2Zr2 tetrahedra,  an edgeedge with one O(3)Sm2Zr2 tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, and edges with four equivalent O(4)Sm2Zr2 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Sm(1) and two equivalent Zr(1) atoms to form OSm2Zr2 tetrahedra that share corners with four equivalent O(3)Sm2Zr2 tetrahedra, corners with four equivalent O(1)Sm4 tetrahedra, corners with six equivalent O(4)Sm2Zr2 tetrahedra,  an edgeedge with one O(4)Sm2Zr2 tetrahedra, and edges with four equivalent O(3)Sm2Zr2 tetrahedra.
Sm4ZrO8 crystallizes in the orthorhombic Immm space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. Both Sm(1)-O(1) bond lengths are 2.52 Å. Both Sm(1)-O(3) bond lengths are 2.32 Å. Both Sm(1)-O(4) bond lengths are 2.26 Å. In the second Sm site, Sm(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing SmO6 octahedra. The corner-sharing octahedral tilt angles are 55°. Both Sm(2)-O(1) bond lengths are 2.45 Å. There are two shorter (2.19 Å) and two longer (2.44 Å) Sm(2)-O(2) bond lengths. Zr(1) is bonded in a body-centered cubic geometry to four equivalent O(3) and four equivalent O(4) atoms. All Zr(1)-O(3) bond lengths are 2.26 Å. All Zr(1)-O(4) bond lengths are 2.33 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sm(1) and two equivalent Sm(2) atoms to form OSm4 tetrahedra that share corners with two equivalent O(3)Sm2Zr2 tetrahedra, corners with four equivalent O(4)Sm2Zr2 tetrahedra, corners with four equivalent O(1)Sm4 tetrahedra, corners with six equivalent O(2)Sm4 tetrahedra,  an edgeedge with one O(3)Sm2Zr2 tetrahedra, and  an edgeedge with one O(2)Sm4 tetrahedra. In the second O site, O(2) is bonded to four equivalent Sm(2) atoms to form a mixture of corner and edge-sharing OSm4 tetrahedra. In the third O site, O(3) is bonded to two equivalent Sm(1) and two equivalent Zr(1) atoms to form OSm2Zr2 tetrahedra that share corners with two equivalent O(1)Sm4 tetrahedra, corners with four equivalent O(4)Sm2Zr2 tetrahedra, corners with six equivalent O(3)Sm2Zr2 tetrahedra,  an edgeedge with one O(3)Sm2Zr2 tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, and edges with four equivalent O(4)Sm2Zr2 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Sm(1) and two equivalent Zr(1) atoms to form OSm2Zr2 tetrahedra that share corners with four equivalent O(3)Sm2Zr2 tetrahedra, corners with four equivalent O(1)Sm4 tetrahedra, corners with six equivalent O(4)Sm2Zr2 tetrahedra,  an edgeedge with one O(4)Sm2Zr2 tetrahedra, and edges with four equivalent O(3)Sm2Zr2 tetrahedra.