Sm3NbO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to one O(3), two equivalent O(1), and four equivalent O(2) atoms to form distorted SmO7 pentagonal bipyramids that share corners with two equivalent Nb(1)O6 octahedra, corners with three equivalent Sm(1)O7 pentagonal bipyramids, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Sm(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 38°. In the second Sm site, Sm(2) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. Nb(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Sm(1)O7 pentagonal bipyramids, and edges with four equivalent Sm(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. There are three 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 a mixture of corner and edge-sharing OSm4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Sm(2), two equivalent Sm(1), and one Nb(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Sm(1) and two equivalent Nb(1) atoms.
Sm3NbO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to one O(3), two equivalent O(1), and four equivalent O(2) atoms to form distorted SmO7 pentagonal bipyramids that share corners with two equivalent Nb(1)O6 octahedra, corners with three equivalent Sm(1)O7 pentagonal bipyramids, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Sm(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 38°. The Sm(1)-O(3) bond length is 2.62 Å. There is one shorter (2.26 Å) and one longer (2.29 Å) Sm(1)-O(1) bond length. There are two shorter (2.39 Å) and two longer (2.44 Å) Sm(1)-O(2) bond lengths. In the second Sm site, Sm(2) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. All Sm(2)-O(1) bond lengths are 2.38 Å. All Sm(2)-O(2) bond lengths are 2.70 Å. Nb(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form NbO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, corners with four equivalent Sm(1)O7 pentagonal bipyramids, and edges with four equivalent Sm(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. Both Nb(1)-O(3) bond lengths are 1.99 Å. All Nb(1)-O(2) bond lengths are 2.00 Å. There are three 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 a mixture of corner and edge-sharing OSm4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Sm(2), two equivalent Sm(1), and one Nb(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Sm(1) and two equivalent Nb(1) atoms.