Mg4FeO5 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/m space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent O(3) and three equivalent O(5) atoms to form MgO6 octahedra that share corners with three equivalent Mg(3)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, edges with three equivalent Mg(3)O6 octahedra, edges with three equivalent Fe(2)O6 octahedra, and edges with six equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the second Mg site, Mg(2) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form MgO6 octahedra that share corners with three equivalent Mg(4)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra, edges with three equivalent Mg(4)O6 octahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with six equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the third Mg site, Mg(3) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. In the fourth Mg site, Mg(4) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to six equivalent O(2) atoms to form FeO6 octahedra that share corners with six equivalent Mg(2)O6 octahedra, edges with six equivalent Mg(2)O6 octahedra, and edges with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 3°. In the second Fe site, Fe(2) is bonded to six equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with six equivalent Mg(1)O6 octahedra, and edges with six equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 3°. There are five inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Mg(3) and three equivalent Mg(4) atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded to three equivalent Mg(2) and three equivalent Fe(1) atoms to form OMg3Fe3 octahedra that share corners with three equivalent O(2)Mg3Fe3 octahedra, corners with three equivalent O(4)Mg6 octahedra, edges with three equivalent O(4)Mg6 octahedra, and edges with nine equivalent O(2)Mg3Fe3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the third O site, O(3) is bonded to three equivalent Mg(1) and three equivalent Fe(2) atoms to form OMg3Fe3 octahedra that share corners with three equivalent O(3)Mg3Fe3 octahedra, corners with three equivalent O(5)Mg6 octahedra, edges with three equivalent O(5)Mg6 octahedra, and edges with nine equivalent O(3)Mg3Fe3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fourth O site, O(4) is bonded to three equivalent Mg(2) and three equivalent Mg(4) atoms to form OMg6 octahedra that share corners with three equivalent O(2)Mg3Fe3 octahedra, corners with three equivalent O(1)Mg6 octahedra, edges with three equivalent O(2)Mg3Fe3 octahedra, edges with three equivalent O(1)Mg6 octahedra, and edges with six equivalent O(4)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fifth O site, O(5) is bonded to three equivalent Mg(1) and three equivalent Mg(3) atoms to form OMg6 octahedra that share corners with three equivalent O(3)Mg3Fe3 octahedra, corners with three equivalent O(1)Mg6 octahedra, edges with three equivalent O(3)Mg3Fe3 octahedra, edges with three equivalent O(1)Mg6 octahedra, and edges with six equivalent O(5)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.
Mg4FeO5 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/m space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to three equivalent O(3) and three equivalent O(5) atoms to form MgO6 octahedra that share corners with three equivalent Mg(3)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, edges with three equivalent Mg(3)O6 octahedra, edges with three equivalent Fe(2)O6 octahedra, and edges with six equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. All Mg(1)-O(3) bond lengths are 2.08 Å. All Mg(1)-O(5) bond lengths are 2.10 Å. In the second Mg site, Mg(2) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form MgO6 octahedra that share corners with three equivalent Mg(4)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra, edges with three equivalent Mg(4)O6 octahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with six equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. There is one shorter (2.08 Å) and two longer (2.09 Å) Mg(2)-O(2) bond lengths. All Mg(2)-O(4) bond lengths are 2.10 Å. In the third Mg site, Mg(3) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. All Mg(3)-O(1) bond lengths are 2.10 Å. All Mg(3)-O(5) bond lengths are 2.10 Å. In the fourth Mg site, Mg(4) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra are not tilted. All Mg(4)-O(1) bond lengths are 2.10 Å. All Mg(4)-O(4) bond lengths are 2.10 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to six equivalent O(2) atoms to form FeO6 octahedra that share corners with six equivalent Mg(2)O6 octahedra, edges with six equivalent Mg(2)O6 octahedra, and edges with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 3°. There are four shorter (2.16 Å) and two longer (2.17 Å) Fe(1)-O(2) bond lengths. In the second Fe site, Fe(2) is bonded to six equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with six equivalent Mg(1)O6 octahedra, and edges with six equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 3°. All Fe(2)-O(3) bond lengths are 2.15 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Mg(3) and three equivalent Mg(4) atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra are not tilted. In the second O site, O(2) is bonded to three equivalent Mg(2) and three equivalent Fe(1) atoms to form OMg3Fe3 octahedra that share corners with three equivalent O(2)Mg3Fe3 octahedra, corners with three equivalent O(4)Mg6 octahedra, edges with three equivalent O(4)Mg6 octahedra, and edges with nine equivalent O(2)Mg3Fe3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the third O site, O(3) is bonded to three equivalent Mg(1) and three equivalent Fe(2) atoms to form OMg3Fe3 octahedra that share corners with three equivalent O(3)Mg3Fe3 octahedra, corners with three equivalent O(5)Mg6 octahedra, edges with three equivalent O(5)Mg6 octahedra, and edges with nine equivalent O(3)Mg3Fe3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fourth O site, O(4) is bonded to three equivalent Mg(2) and three equivalent Mg(4) atoms to form OMg6 octahedra that share corners with three equivalent O(2)Mg3Fe3 octahedra, corners with three equivalent O(1)Mg6 octahedra, edges with three equivalent O(2)Mg3Fe3 octahedra, edges with three equivalent O(1)Mg6 octahedra, and edges with six equivalent O(4)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fifth O site, O(5) is bonded to three equivalent Mg(1) and three equivalent Mg(3) atoms to form OMg6 octahedra that share corners with three equivalent O(3)Mg3Fe3 octahedra, corners with three equivalent O(1)Mg6 octahedra, edges with three equivalent O(3)Mg3Fe3 octahedra, edges with three equivalent O(1)Mg6 octahedra, and edges with six equivalent O(5)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.