Sm2ScTaO7 crystallizes in the orthorhombic Imma space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to two equivalent O(1), two equivalent O(4), and four equivalent O(2) atoms to form distorted SmO8 hexagonal bipyramids that share edges with two equivalent Sm(1)O8 hexagonal bipyramids, edges with two equivalent Sc(1)O6 octahedra, and edges with four equivalent Ta(1)O6 octahedra. In the second Sm site, Sm(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. Sc(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form ScO6 octahedra that share corners with two equivalent Sc(1)O6 octahedra, corners with four equivalent Ta(1)O6 octahedra, and edges with two equivalent Sm(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 51-58°. Ta(1) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Sc(1)O6 octahedra, and edges with four equivalent Sm(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 41-51°. 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)Sm2Sc2 tetrahedra, corners with four equivalent O(1)Sm4 tetrahedra, corners with eight equivalent O(2)Sm2ScTa tetrahedra,  an edgeedge with one O(3)Sm2Sc2 tetrahedra, and edges with four equivalent O(2)Sm2ScTa tetrahedra. In the second O site, O(2) is bonded to one Sm(1), one Sm(2), one Sc(1), and one Ta(1) atom to form distorted OSm2ScTa tetrahedra that share corners with two equivalent O(3)Sm2Sc2 tetrahedra, corners with two equivalent O(1)Sm4 tetrahedra, corners with eight equivalent O(2)Sm2ScTa tetrahedra,  an edgeedge with one O(3)Sm2Sc2 tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, and edges with two equivalent O(2)Sm2ScTa tetrahedra. In the third O site, O(3) is bonded to two equivalent Sm(2) and two equivalent Sc(1) atoms to form OSm2Sc2 tetrahedra that share corners with two equivalent O(1)Sm4 tetrahedra, corners with four equivalent O(3)Sm2Sc2 tetrahedra, corners with eight equivalent O(2)Sm2ScTa tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, and edges with four equivalent O(2)Sm2ScTa tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Sm(1) and two equivalent Ta(1) atoms.
Sm2ScTaO7 crystallizes in the orthorhombic Imma space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to two equivalent O(1), two equivalent O(4), and four equivalent O(2) atoms to form distorted SmO8 hexagonal bipyramids that share edges with two equivalent Sm(1)O8 hexagonal bipyramids, edges with two equivalent Sc(1)O6 octahedra, and edges with four equivalent Ta(1)O6 octahedra. Both Sm(1)-O(1) bond lengths are 2.25 Å. Both Sm(1)-O(4) bond lengths are 2.68 Å. All Sm(1)-O(2) bond lengths are 2.53 Å. In the second Sm site, Sm(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. Both Sm(2)-O(1) bond lengths are 2.32 Å. Both Sm(2)-O(3) bond lengths are 2.48 Å. All Sm(2)-O(2) bond lengths are 2.61 Å. Sc(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form ScO6 octahedra that share corners with two equivalent Sc(1)O6 octahedra, corners with four equivalent Ta(1)O6 octahedra, and edges with two equivalent Sm(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 51-58°. Both Sc(1)-O(3) bond lengths are 2.12 Å. All Sc(1)-O(2) bond lengths are 2.14 Å. Ta(1) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Sc(1)O6 octahedra, and edges with four equivalent Sm(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 41-51°. Both Ta(1)-O(4) bond lengths are 2.01 Å. All Ta(1)-O(2) bond lengths are 1.99 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)Sm2Sc2 tetrahedra, corners with four equivalent O(1)Sm4 tetrahedra, corners with eight equivalent O(2)Sm2ScTa tetrahedra,  an edgeedge with one O(3)Sm2Sc2 tetrahedra, and edges with four equivalent O(2)Sm2ScTa tetrahedra. In the second O site, O(2) is bonded to one Sm(1), one Sm(2), one Sc(1), and one Ta(1) atom to form distorted OSm2ScTa tetrahedra that share corners with two equivalent O(3)Sm2Sc2 tetrahedra, corners with two equivalent O(1)Sm4 tetrahedra, corners with eight equivalent O(2)Sm2ScTa tetrahedra,  an edgeedge with one O(3)Sm2Sc2 tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, and edges with two equivalent O(2)Sm2ScTa tetrahedra. In the third O site, O(3) is bonded to two equivalent Sm(2) and two equivalent Sc(1) atoms to form OSm2Sc2 tetrahedra that share corners with two equivalent O(1)Sm4 tetrahedra, corners with four equivalent O(3)Sm2Sc2 tetrahedra, corners with eight equivalent O(2)Sm2ScTa tetrahedra,  an edgeedge with one O(1)Sm4 tetrahedra, and edges with four equivalent O(2)Sm2ScTa tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Sm(1) and two equivalent Ta(1) atoms.