Sm3ReO8 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and two equivalent O(8) atoms. In the second Sm site, Sm(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and two equivalent O(7) atoms. In the third Sm site, Sm(3) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(7), one O(8), two equivalent O(5), and two equivalent O(6) atoms. Re(1) is bonded in an octahedral geometry to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom. There are eight inequivalent O sites. In the first O site, O(5) is bonded to one Sm(1), one Sm(2), and two equivalent Sm(3) atoms to form distorted OSm4 tetrahedra that share corners with two equivalent O(7)Sm3Re tetrahedra, corners with two equivalent O(5)Sm4 tetrahedra, corners with four equivalent O(2)Sm3Re trigonal pyramids,  an edgeedge with one O(7)Sm3Re tetrahedra, and edges with three equivalent O(6)Sm4 tetrahedra. In the second O site, O(6) is bonded to one Sm(1), one Sm(2), and two equivalent Sm(3) atoms to form distorted OSm4 tetrahedra that share corners with two equivalent O(6)Sm4 tetrahedra, corners with four equivalent O(7)Sm3Re tetrahedra, corners with four equivalent O(2)Sm3Re trigonal pyramids, and edges with three equivalent O(5)Sm4 tetrahedra. In the third O site, O(7) is bonded to one Sm(3), two equivalent Sm(2), and one Re(1) atom to form distorted OSm3Re tetrahedra that share corners with two equivalent O(5)Sm4 tetrahedra, corners with four equivalent O(6)Sm4 tetrahedra, corners with two equivalent O(2)Sm3Re trigonal pyramids,  an edgeedge with one O(7)Sm3Re tetrahedra,  an edgeedge with one O(5)Sm4 tetrahedra, and  an edgeedge with one O(2)Sm3Re trigonal pyramid. In the fourth O site, O(8) is bonded in a 4-coordinate geometry to one Sm(3), two equivalent Sm(1), and one Re(1) atom. In the fifth O site, O(1) is bonded in a distorted single-bond geometry to one Sm(1), one Sm(2), and one Re(1) atom. In the sixth O site, O(2) is bonded to one Sm(1), one Sm(2), one Sm(3), and one Re(1) atom to form distorted OSm3Re trigonal pyramids that share corners with two equivalent O(7)Sm3Re tetrahedra, corners with four equivalent O(5)Sm4 tetrahedra, corners with four equivalent O(6)Sm4 tetrahedra, and  an edgeedge with one O(7)Sm3Re tetrahedra. In the seventh O site, O(3) is bonded in a 4-coordinate geometry to one Sm(1), one Sm(2), one Sm(3), and one Re(1) atom. In the eighth O site, O(4) is bonded in a 3-coordinate geometry to one Sm(1), one Sm(2), and one Re(1) atom.
Sm3ReO8 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and two equivalent O(8) atoms. The Sm(1)-O(1) bond length is 2.60 Å. The Sm(1)-O(2) bond length is 2.59 Å. The Sm(1)-O(3) bond length is 2.41 Å. The Sm(1)-O(4) bond length is 2.30 Å. The Sm(1)-O(5) bond length is 2.29 Å. The Sm(1)-O(6) bond length is 2.29 Å. There is one shorter (2.44 Å) and one longer (2.59 Å) Sm(1)-O(8) bond length. In the second Sm site, Sm(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and two equivalent O(7) atoms. The Sm(2)-O(1) bond length is 2.61 Å. The Sm(2)-O(2) bond length is 2.59 Å. The Sm(2)-O(3) bond length is 2.44 Å. The Sm(2)-O(4) bond length is 2.33 Å. The Sm(2)-O(5) bond length is 2.30 Å. The Sm(2)-O(6) bond length is 2.23 Å. There is one shorter (2.44 Å) and one longer (2.59 Å) Sm(2)-O(7) bond length. In the third Sm site, Sm(3) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(7), one O(8), two equivalent O(5), and two equivalent O(6) atoms. The Sm(3)-O(2) bond length is 2.52 Å. The Sm(3)-O(3) bond length is 2.65 Å. The Sm(3)-O(7) bond length is 2.58 Å. The Sm(3)-O(8) bond length is 2.61 Å. There is one shorter (2.38 Å) and one longer (2.42 Å) Sm(3)-O(5) bond length. There is one shorter (2.34 Å) and one longer (2.41 Å) Sm(3)-O(6) bond length. Re(1) is bonded in an octahedral geometry to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom. The Re(1)-O(1) bond length is 1.82 Å. The Re(1)-O(2) bond length is 1.90 Å. The Re(1)-O(3) bond length is 1.96 Å. The Re(1)-O(4) bond length is 1.85 Å. The Re(1)-O(7) bond length is 1.89 Å. The Re(1)-O(8) bond length is 1.91 Å. There are eight inequivalent O sites. In the first O site, O(5) is bonded to one Sm(1), one Sm(2), and two equivalent Sm(3) atoms to form distorted OSm4 tetrahedra that share corners with two equivalent O(7)Sm3Re tetrahedra, corners with two equivalent O(5)Sm4 tetrahedra, corners with four equivalent O(2)Sm3Re trigonal pyramids,  an edgeedge with one O(7)Sm3Re tetrahedra, and edges with three equivalent O(6)Sm4 tetrahedra. In the second O site, O(6) is bonded to one Sm(1), one Sm(2), and two equivalent Sm(3) atoms to form distorted OSm4 tetrahedra that share corners with two equivalent O(6)Sm4 tetrahedra, corners with four equivalent O(7)Sm3Re tetrahedra, corners with four equivalent O(2)Sm3Re trigonal pyramids, and edges with three equivalent O(5)Sm4 tetrahedra. In the third O site, O(7) is bonded to one Sm(3), two equivalent Sm(2), and one Re(1) atom to form distorted OSm3Re tetrahedra that share corners with two equivalent O(5)Sm4 tetrahedra, corners with four equivalent O(6)Sm4 tetrahedra, corners with two equivalent O(2)Sm3Re trigonal pyramids,  an edgeedge with one O(7)Sm3Re tetrahedra,  an edgeedge with one O(5)Sm4 tetrahedra, and  an edgeedge with one O(2)Sm3Re trigonal pyramid. In the fourth O site, O(8) is bonded in a 4-coordinate geometry to one Sm(3), two equivalent Sm(1), and one Re(1) atom. In the fifth O site, O(1) is bonded in a distorted single-bond geometry to one Sm(1), one Sm(2), and one Re(1) atom. In the sixth O site, O(2) is bonded to one Sm(1), one Sm(2), one Sm(3), and one Re(1) atom to form distorted OSm3Re trigonal pyramids that share corners with two equivalent O(7)Sm3Re tetrahedra, corners with four equivalent O(5)Sm4 tetrahedra, corners with four equivalent O(6)Sm4 tetrahedra, and  an edgeedge with one O(7)Sm3Re tetrahedra. In the seventh O site, O(3) is bonded in a 4-coordinate geometry to one Sm(1), one Sm(2), one Sm(3), and one Re(1) atom. In the eighth O site, O(4) is bonded in a 3-coordinate geometry to one Sm(1), one Sm(2), and one Re(1) atom.