Mg4CuO5 is Caswellsilverite-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(2), one O(3), and four equivalent O(1) atoms to form MgO6 octahedra that share  a cornercorner with one Mg(2)O6 octahedra, corners with five equivalent Mg(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with four equivalent Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the second Mg site, Mg(2) is bonded to one O(1) and five equivalent O(3) atoms to form MgO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Cu(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(2)O6 octahedra. The corner-sharing octahedra are not tilted. Cu(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form CuO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Cu(1)O6 octahedra, edges with four equivalent Cu(1)O6 octahedra, and edges with eight equivalent Mg(1)O6 octahedra. The corner-sharing octahedra are not tilted. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), four equivalent Mg(1), and one Cu(1) atom to form OMg5Cu octahedra that share  a cornercorner with one O(3)Mg6 octahedra, corners with five equivalent O(1)Mg5Cu octahedra, edges with four equivalent O(2)Mg2Cu4 octahedra, edges with four equivalent O(1)Mg5Cu octahedra, and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the second O site, O(2) is bonded to two equivalent Mg(1) and four equivalent Cu(1) atoms to form OMg2Cu4 octahedra that share corners with two equivalent O(3)Mg6 octahedra, corners with four equivalent O(2)Mg2Cu4 octahedra, edges with four equivalent O(2)Mg2Cu4 octahedra, and edges with eight equivalent O(1)Mg5Cu octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to one Mg(1) and five equivalent Mg(2) atoms to form OMg6 octahedra that share  a cornercorner with one O(2)Mg2Cu4 octahedra,  a cornercorner with one O(1)Mg5Cu octahedra, corners with four equivalent O(3)Mg6 octahedra, edges with four equivalent O(1)Mg5Cu octahedra, and edges with eight equivalent O(3)Mg6 octahedra. The corner-sharing octahedra are not tilted.
Mg4CuO5 is Caswellsilverite-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(2), one O(3), and four equivalent O(1) atoms to form MgO6 octahedra that share  a cornercorner with one Mg(2)O6 octahedra, corners with five equivalent Mg(1)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, edges with four equivalent Mg(2)O6 octahedra, and edges with four equivalent Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. The Mg(1)-O(2) bond length is 2.10 Å. The Mg(1)-O(3) bond length is 2.15 Å. All Mg(1)-O(1) bond lengths are 2.13 Å. In the second Mg site, Mg(2) is bonded to one O(1) and five equivalent O(3) atoms to form MgO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Cu(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with eight equivalent Mg(2)O6 octahedra. The corner-sharing octahedra are not tilted. The Mg(2)-O(1) bond length is 2.11 Å. There is one shorter (2.12 Å) and four longer (2.13 Å) Mg(2)-O(3) bond lengths. Cu(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form CuO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with four equivalent Cu(1)O6 octahedra, edges with four equivalent Cu(1)O6 octahedra, and edges with eight equivalent Mg(1)O6 octahedra. The corner-sharing octahedra are not tilted. Both Cu(1)-O(1) bond lengths are 2.14 Å. All Cu(1)-O(2) bond lengths are 2.13 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), four equivalent Mg(1), and one Cu(1) atom to form OMg5Cu octahedra that share  a cornercorner with one O(3)Mg6 octahedra, corners with five equivalent O(1)Mg5Cu octahedra, edges with four equivalent O(2)Mg2Cu4 octahedra, edges with four equivalent O(1)Mg5Cu octahedra, and edges with four equivalent O(3)Mg6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the second O site, O(2) is bonded to two equivalent Mg(1) and four equivalent Cu(1) atoms to form OMg2Cu4 octahedra that share corners with two equivalent O(3)Mg6 octahedra, corners with four equivalent O(2)Mg2Cu4 octahedra, edges with four equivalent O(2)Mg2Cu4 octahedra, and edges with eight equivalent O(1)Mg5Cu octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to one Mg(1) and five equivalent Mg(2) atoms to form OMg6 octahedra that share  a cornercorner with one O(2)Mg2Cu4 octahedra,  a cornercorner with one O(1)Mg5Cu octahedra, corners with four equivalent O(3)Mg6 octahedra, edges with four equivalent O(1)Mg5Cu octahedra, and edges with eight equivalent O(3)Mg6 octahedra. The corner-sharing octahedra are not tilted.