Sm(FeO2)2 is Aluminum carbonitride-like structured and crystallizes in the trigonal R3m space group. Sm(1) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form distorted SmO6 octahedra that share corners with three equivalent Fe(1)O5 trigonal bipyramids, corners with three equivalent Fe(2)O5 trigonal bipyramids, and edges with six equivalent Sm(1)O6 octahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), and three equivalent O(4) atoms to form FeO5 trigonal bipyramids that share corners with three equivalent Sm(1)O6 octahedra, corners with six equivalent Fe(1)O5 trigonal bipyramids, and edges with three equivalent Fe(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 64°. In the second Fe site, Fe(2) is bonded to one O(3), one O(4), and three equivalent O(1) atoms to form FeO5 trigonal bipyramids that share corners with three equivalent Sm(1)O6 octahedra, corners with six equivalent Fe(2)O5 trigonal bipyramids, and edges with three equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Fe(1) and three equivalent Fe(2) atoms to form OFe4 trigonal pyramids that share  a cornercorner with one O(2)Sm3Fe tetrahedra, corners with three equivalent O(3)Sm3Fe tetrahedra, corners with six equivalent O(1)Fe4 trigonal pyramids, and edges with three equivalent O(4)Fe4 trigonal pyramids. In the second O site, O(2) is bonded to three equivalent Sm(1) and one Fe(1) atom to form OSm3Fe tetrahedra that share corners with three equivalent O(3)Sm3Fe tetrahedra, corners with six equivalent O(2)Sm3Fe tetrahedra,  a cornercorner with one O(1)Fe4 trigonal pyramid, corners with three equivalent O(4)Fe4 trigonal pyramids, and edges with three equivalent O(3)Sm3Fe tetrahedra. In the third O site, O(3) is bonded to three equivalent Sm(1) and one Fe(2) atom to form OSm3Fe tetrahedra that share corners with three equivalent O(2)Sm3Fe tetrahedra, corners with six equivalent O(3)Sm3Fe tetrahedra,  a cornercorner with one O(4)Fe4 trigonal pyramid, corners with three equivalent O(1)Fe4 trigonal pyramids, and edges with three equivalent O(2)Sm3Fe tetrahedra. In the fourth O site, O(4) is bonded to one Fe(2) and three equivalent Fe(1) atoms to form OFe4 trigonal pyramids that share  a cornercorner with one O(3)Sm3Fe tetrahedra, corners with three equivalent O(2)Sm3Fe tetrahedra, corners with six equivalent O(4)Fe4 trigonal pyramids, and edges with three equivalent O(1)Fe4 trigonal pyramids.
Sm(FeO2)2 is Aluminum carbonitride-like structured and crystallizes in the trigonal R3m space group. Sm(1) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form distorted SmO6 octahedra that share corners with three equivalent Fe(1)O5 trigonal bipyramids, corners with three equivalent Fe(2)O5 trigonal bipyramids, and edges with six equivalent Sm(1)O6 octahedra. All Sm(1)-O(2) bond lengths are 2.33 Å. All Sm(1)-O(3) bond lengths are 2.36 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), and three equivalent O(4) atoms to form FeO5 trigonal bipyramids that share corners with three equivalent Sm(1)O6 octahedra, corners with six equivalent Fe(1)O5 trigonal bipyramids, and edges with three equivalent Fe(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 64°. The Fe(1)-O(1) bond length is 2.26 Å. The Fe(1)-O(2) bond length is 2.04 Å. All Fe(1)-O(4) bond lengths are 2.11 Å. In the second Fe site, Fe(2) is bonded to one O(3), one O(4), and three equivalent O(1) atoms to form FeO5 trigonal bipyramids that share corners with three equivalent Sm(1)O6 octahedra, corners with six equivalent Fe(2)O5 trigonal bipyramids, and edges with three equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. The Fe(2)-O(3) bond length is 1.93 Å. The Fe(2)-O(4) bond length is 1.97 Å. All Fe(2)-O(1) bond lengths are 2.09 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Fe(1) and three equivalent Fe(2) atoms to form OFe4 trigonal pyramids that share  a cornercorner with one O(2)Sm3Fe tetrahedra, corners with three equivalent O(3)Sm3Fe tetrahedra, corners with six equivalent O(1)Fe4 trigonal pyramids, and edges with three equivalent O(4)Fe4 trigonal pyramids. In the second O site, O(2) is bonded to three equivalent Sm(1) and one Fe(1) atom to form OSm3Fe tetrahedra that share corners with three equivalent O(3)Sm3Fe tetrahedra, corners with six equivalent O(2)Sm3Fe tetrahedra,  a cornercorner with one O(1)Fe4 trigonal pyramid, corners with three equivalent O(4)Fe4 trigonal pyramids, and edges with three equivalent O(3)Sm3Fe tetrahedra. In the third O site, O(3) is bonded to three equivalent Sm(1) and one Fe(2) atom to form OSm3Fe tetrahedra that share corners with three equivalent O(2)Sm3Fe tetrahedra, corners with six equivalent O(3)Sm3Fe tetrahedra,  a cornercorner with one O(4)Fe4 trigonal pyramid, corners with three equivalent O(1)Fe4 trigonal pyramids, and edges with three equivalent O(2)Sm3Fe tetrahedra. In the fourth O site, O(4) is bonded to one Fe(2) and three equivalent Fe(1) atoms to form OFe4 trigonal pyramids that share  a cornercorner with one O(3)Sm3Fe tetrahedra, corners with three equivalent O(2)Sm3Fe tetrahedra, corners with six equivalent O(4)Fe4 trigonal pyramids, and edges with three equivalent O(1)Fe4 trigonal pyramids.