Li4Fe5SbO12 crystallizes in the monoclinic C2/m space group. Li(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(3), and two equivalent O(2) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form edge-sharing FeO6 octahedra. In the second Fe site, Fe(2) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form FeO6 octahedra that share edges with three equivalent Fe(2)O6 octahedra and edges with three equivalent Sb(1)O6 octahedra. In the third Fe site, Fe(3) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form edge-sharing FeO6 octahedra. Sb(1) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form SbO6 octahedra that share edges with six equivalent Fe(2)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), two equivalent Fe(2), and one Sb(1) atom to form distorted OLiFe2Sb trigonal pyramids that share  a cornercorner with one O(3)Li2Fe3 square pyramid, corners with two equivalent O(2)Li2Fe3 square pyramids, corners with five equivalent O(1)LiFe2Sb trigonal pyramids, and edges with two equivalent O(1)LiFe2Sb trigonal pyramids. In the second O site, O(2) is bonded to two equivalent Li(1), one Fe(3), and two equivalent Fe(1) atoms to form OLi2Fe3 square pyramids that share corners with two equivalent O(3)Li2Fe3 square pyramids, corners with three equivalent O(2)Li2Fe3 square pyramids, corners with two equivalent O(1)LiFe2Sb trigonal pyramids, edges with three equivalent O(3)Li2Fe3 square pyramids, and edges with four equivalent O(2)Li2Fe3 square pyramids. In the third O site, O(3) is bonded to two equivalent Li(1), one Fe(3), and two equivalent Fe(1) atoms to form OLi2Fe3 square pyramids that share  a cornercorner with one O(3)Li2Fe3 square pyramid, corners with four equivalent O(2)Li2Fe3 square pyramids, corners with two equivalent O(1)LiFe2Sb trigonal pyramids,  an edgeedge with one O(3)Li2Fe3 square pyramid, and edges with six equivalent O(2)Li2Fe3 square pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Fe(2) and one Sb(1) atom.
Li4Fe5SbO12 crystallizes in the monoclinic C2/m space group. Li(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(3), and two equivalent O(2) atoms. The Li(1)-O(1) bond length is 2.02 Å. The Li(1)-O(3) bond length is 2.05 Å. Both Li(1)-O(2) bond lengths are 2.01 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form edge-sharing FeO6 octahedra. Both Fe(1)-O(3) bond lengths are 2.07 Å. There are two shorter (2.04 Å) and two longer (2.09 Å) Fe(1)-O(2) bond lengths. In the second Fe site, Fe(2) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form FeO6 octahedra that share edges with three equivalent Fe(2)O6 octahedra and edges with three equivalent Sb(1)O6 octahedra. Both Fe(2)-O(4) bond lengths are 1.96 Å. There are two shorter (1.98 Å) and two longer (2.00 Å) Fe(2)-O(1) bond lengths. In the third Fe site, Fe(3) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form edge-sharing FeO6 octahedra. Both Fe(3)-O(3) bond lengths are 2.00 Å. All Fe(3)-O(2) bond lengths are 2.10 Å. Sb(1) is bonded to two equivalent O(4) and four equivalent O(1) atoms to form SbO6 octahedra that share edges with six equivalent Fe(2)O6 octahedra. Both Sb(1)-O(4) bond lengths are 2.02 Å. All Sb(1)-O(1) bond lengths are 2.04 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), two equivalent Fe(2), and one Sb(1) atom to form distorted OLiFe2Sb trigonal pyramids that share  a cornercorner with one O(3)Li2Fe3 square pyramid, corners with two equivalent O(2)Li2Fe3 square pyramids, corners with five equivalent O(1)LiFe2Sb trigonal pyramids, and edges with two equivalent O(1)LiFe2Sb trigonal pyramids. In the second O site, O(2) is bonded to two equivalent Li(1), one Fe(3), and two equivalent Fe(1) atoms to form OLi2Fe3 square pyramids that share corners with two equivalent O(3)Li2Fe3 square pyramids, corners with three equivalent O(2)Li2Fe3 square pyramids, corners with two equivalent O(1)LiFe2Sb trigonal pyramids, edges with three equivalent O(3)Li2Fe3 square pyramids, and edges with four equivalent O(2)Li2Fe3 square pyramids. In the third O site, O(3) is bonded to two equivalent Li(1), one Fe(3), and two equivalent Fe(1) atoms to form OLi2Fe3 square pyramids that share  a cornercorner with one O(3)Li2Fe3 square pyramid, corners with four equivalent O(2)Li2Fe3 square pyramids, corners with two equivalent O(1)LiFe2Sb trigonal pyramids,  an edgeedge with one O(3)Li2Fe3 square pyramid, and edges with six equivalent O(2)Li2Fe3 square pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Fe(2) and one Sb(1) atom.