LiEu2SmO4 crystallizes in the orthorhombic Pnma space group. Li(1) is bonded to one O(1), one O(4), and two equivalent O(2) atoms to form LiO4 tetrahedra that share  a cornercorner with one Sm(1)O6 octahedra, corners with two equivalent Li(1)O4 tetrahedra, edges with two equivalent Sm(1)O6 octahedra, and edges with two equivalent Eu(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 2°. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 6-coordinate geometry to one O(4), two equivalent O(1), and three equivalent O(2) atoms. In the second Eu site, Eu(2) is bonded to two equivalent O(1), two equivalent O(4), and three equivalent O(3) atoms to form distorted EuO7 pentagonal bipyramids that share corners with four equivalent Sm(1)O6 octahedra, edges with four equivalent Sm(1)O6 octahedra, edges with two equivalent Eu(2)O7 pentagonal bipyramids, edges with two equivalent Li(1)O4 tetrahedra, and faces with two equivalent Eu(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 13-17°. Sm(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form SmO6 octahedra that share corners with four equivalent Eu(2)O7 pentagonal bipyramids,  a cornercorner with one Li(1)O4 tetrahedra, edges with two equivalent Sm(1)O6 octahedra, edges with four equivalent Eu(2)O7 pentagonal bipyramids, and edges with two equivalent Li(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), two equivalent Eu(1), two equivalent Eu(2), and one Sm(1) atom to form distorted OLiSmEu4 octahedra that share corners with two equivalent O(3)Sm2Eu3 square pyramids, edges with two equivalent O(1)LiSmEu4 octahedra, and edges with three equivalent O(3)Sm2Eu3 square pyramids. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Li(1), three equivalent Eu(1), and one Sm(1) atom. In the third O site, O(3) is bonded to three equivalent Eu(2) and two equivalent Sm(1) atoms to form distorted OSm2Eu3 square pyramids that share corners with two equivalent O(1)LiSmEu4 octahedra, edges with three equivalent O(1)LiSmEu4 octahedra, and edges with four equivalent O(3)Sm2Eu3 square pyramids. The corner-sharing octahedral tilt angles are 19°. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Li(1), one Eu(1), two equivalent Eu(2), and two equivalent Sm(1) atoms.
LiEu2SmO4 crystallizes in the orthorhombic Pnma space group. Li(1) is bonded to one O(1), one O(4), and two equivalent O(2) atoms to form LiO4 tetrahedra that share  a cornercorner with one Sm(1)O6 octahedra, corners with two equivalent Li(1)O4 tetrahedra, edges with two equivalent Sm(1)O6 octahedra, and edges with two equivalent Eu(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 2°. The Li(1)-O(1) bond length is 1.88 Å. The Li(1)-O(4) bond length is 1.96 Å. Both Li(1)-O(2) bond lengths are 2.07 Å. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 6-coordinate geometry to one O(4), two equivalent O(1), and three equivalent O(2) atoms. The Eu(1)-O(4) bond length is 2.54 Å. Both Eu(1)-O(1) bond lengths are 2.56 Å. There are two shorter (2.53 Å) and one longer (2.64 Å) Eu(1)-O(2) bond length. In the second Eu site, Eu(2) is bonded to two equivalent O(1), two equivalent O(4), and three equivalent O(3) atoms to form distorted EuO7 pentagonal bipyramids that share corners with four equivalent Sm(1)O6 octahedra, edges with four equivalent Sm(1)O6 octahedra, edges with two equivalent Eu(2)O7 pentagonal bipyramids, edges with two equivalent Li(1)O4 tetrahedra, and faces with two equivalent Eu(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 13-17°. Both Eu(2)-O(1) bond lengths are 2.64 Å. Both Eu(2)-O(4) bond lengths are 2.72 Å. There are two shorter (2.62 Å) and one longer (2.68 Å) Eu(2)-O(3) bond length. Sm(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form SmO6 octahedra that share corners with four equivalent Eu(2)O7 pentagonal bipyramids,  a cornercorner with one Li(1)O4 tetrahedra, edges with two equivalent Sm(1)O6 octahedra, edges with four equivalent Eu(2)O7 pentagonal bipyramids, and edges with two equivalent Li(1)O4 tetrahedra. The Sm(1)-O(1) bond length is 2.32 Å. The Sm(1)-O(2) bond length is 2.39 Å. Both Sm(1)-O(3) bond lengths are 2.38 Å. Both Sm(1)-O(4) bond lengths are 2.41 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), two equivalent Eu(1), two equivalent Eu(2), and one Sm(1) atom to form distorted OLiSmEu4 octahedra that share corners with two equivalent O(3)Sm2Eu3 square pyramids, edges with two equivalent O(1)LiSmEu4 octahedra, and edges with three equivalent O(3)Sm2Eu3 square pyramids. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Li(1), three equivalent Eu(1), and one Sm(1) atom. In the third O site, O(3) is bonded to three equivalent Eu(2) and two equivalent Sm(1) atoms to form distorted OSm2Eu3 square pyramids that share corners with two equivalent O(1)LiSmEu4 octahedra, edges with three equivalent O(1)LiSmEu4 octahedra, and edges with four equivalent O(3)Sm2Eu3 square pyramids. The corner-sharing octahedral tilt angles are 19°. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Li(1), one Eu(1), two equivalent Eu(2), and two equivalent Sm(1) atoms.