Sm(FeO2)2 crystallizes in the trigonal R-3m space group. Sm(1) is bonded to six equivalent O(2) atoms to form distorted SmO6 octahedra that share corners with six equivalent Fe(1)O5 trigonal bipyramids and edges with six equivalent Sm(1)O6 octahedra. Fe(1) is bonded to one O(2) and four equivalent O(1) 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(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Fe(1) atoms to form OFe4 trigonal pyramids that share corners with four equivalent O(2)Sm3Fe tetrahedra, corners with six equivalent O(1)Fe4 trigonal pyramids, and edges with three equivalent O(1)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 nine equivalent O(2)Sm3Fe tetrahedra, corners with four equivalent O(1)Fe4 trigonal pyramids, and edges with three equivalent O(2)Sm3Fe tetrahedra.
Sm(FeO2)2 crystallizes in the trigonal R-3m space group. Sm(1) is bonded to six equivalent O(2) atoms to form distorted SmO6 octahedra that share corners with six equivalent Fe(1)O5 trigonal bipyramids and edges with six equivalent Sm(1)O6 octahedra. All Sm(1)-O(2) bond lengths are 2.34 Å. Fe(1) is bonded to one O(2) and four equivalent O(1) 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(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. The Fe(1)-O(2) bond length is 1.95 Å. There is one shorter (2.08 Å) and three longer (2.09 Å) Fe(1)-O(1) bond lengths. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Fe(1) atoms to form OFe4 trigonal pyramids that share corners with four equivalent O(2)Sm3Fe tetrahedra, corners with six equivalent O(1)Fe4 trigonal pyramids, and edges with three equivalent O(1)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 nine equivalent O(2)Sm3Fe tetrahedra, corners with four equivalent O(1)Fe4 trigonal pyramids, and edges with three equivalent O(2)Sm3Fe tetrahedra.