MgSm4(Cu2O5)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form MgO6 octahedra that share  a cornercorner with one Cu(2)O5 square pyramid, corners with two equivalent Cu(3)O4 tetrahedra, and  an edgeedge with one Cu(3)O4 tetrahedra. There are four inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(7), and one O(9) atom. In the second Sm site, Sm(2) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(6), and one O(8) atom. In the third Sm site, Sm(3) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(3), one O(4), one O(5), and one O(7) atom. In the fourth Sm site, Sm(4) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), one O(8), and one O(9) atom. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), one O(4), and one O(5) atom. In the second Cu site, Cu(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form distorted CuO5 square pyramids that share  a cornercorner with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 44°. In the third Cu site, Cu(3) is bonded to one O(10), one O(5), one O(8), and one O(9) atom to form distorted CuO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 8-42°. In the fourth Cu site, Cu(4) is bonded in a 2-coordinate geometry to one O(10), one O(6), and one O(9) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Sm(1), one Sm(2), one Sm(4), one Cu(1), and one Cu(2) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Sm(1), one Sm(2), one Sm(3), one Sm(4), one Cu(1), and one Cu(2) atom. In the third O site, O(3) is bonded to one Sm(1), one Sm(2), one Sm(3), one Sm(4), one Cu(1), and one Cu(2) atom to form distorted OSm4Cu2 octahedra that share corners with two equivalent O(10)Sm2MgCu2 trigonal bipyramids, corners with two equivalent O(8)Sm2MgCu trigonal pyramids, and faces with two equivalent O(4)Sm4Cu2 octahedra. In the fourth O site, O(4) is bonded to one Sm(1), one Sm(2), one Sm(3), one Sm(4), one Cu(1), and one Cu(2) atom to form distorted OSm4Cu2 octahedra that share corners with two equivalent O(10)Sm2MgCu2 trigonal bipyramids,  an edgeedge with one O(8)Sm2MgCu trigonal pyramid, and faces with two equivalent O(3)Sm4Cu2 octahedra. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Mg(1), one Sm(1), one Sm(3), one Cu(1), and one Cu(3) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Mg(1), one Sm(2), one Sm(4), and one Cu(4) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Mg(1), one Sm(1), one Sm(3), and one Cu(2) atom. In the eighth O site, O(8) is bonded to one Mg(1), one Sm(2), one Sm(4), and one Cu(3) atom to form OSm2MgCu trigonal pyramids that share corners with two equivalent O(3)Sm4Cu2 octahedra,  a cornercorner with one O(10)Sm2MgCu2 trigonal bipyramid,  an edgeedge with one O(4)Sm4Cu2 octahedra, and  an edgeedge with one O(10)Sm2MgCu2 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 57-95°. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one Mg(1), one Sm(1), one Sm(4), one Cu(3), and one Cu(4) atom. In the tenth O site, O(10) is bonded to one Mg(1), one Sm(2), one Sm(3), one Cu(3), and one Cu(4) atom to form distorted OSm2MgCu2 trigonal bipyramids that share corners with two equivalent O(3)Sm4Cu2 octahedra, corners with two equivalent O(4)Sm4Cu2 octahedra,  a cornercorner with one O(8)Sm2MgCu trigonal pyramid, and  an edgeedge with one O(8)Sm2MgCu trigonal pyramid. The corner-sharing octahedral tilt angles range from 16-73°.
MgSm4(Cu2O5)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(10), one O(5), one O(6), one O(7), one O(8), and one O(9) atom to form MgO6 octahedra that share  a cornercorner with one Cu(2)O5 square pyramid, corners with two equivalent Cu(3)O4 tetrahedra, and  an edgeedge with one Cu(3)O4 tetrahedra. The Mg(1)-O(10) bond length is 2.15 Å. The Mg(1)-O(5) bond length is 2.11 Å. The Mg(1)-O(6) bond length is 2.16 Å. The Mg(1)-O(7) bond length is 2.09 Å. The Mg(1)-O(8) bond length is 2.11 Å. The Mg(1)-O(9) bond length is 2.08 Å. There are four inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(7), and one O(9) atom. The Sm(1)-O(1) bond length is 2.52 Å. The Sm(1)-O(2) bond length is 2.56 Å. The Sm(1)-O(3) bond length is 2.58 Å. The Sm(1)-O(4) bond length is 2.43 Å. The Sm(1)-O(5) bond length is 2.34 Å. The Sm(1)-O(7) bond length is 2.37 Å. The Sm(1)-O(9) bond length is 2.38 Å. In the second Sm site, Sm(2) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(6), and one O(8) atom. The Sm(2)-O(1) bond length is 2.44 Å. The Sm(2)-O(10) bond length is 2.28 Å. The Sm(2)-O(2) bond length is 2.99 Å. The Sm(2)-O(3) bond length is 2.74 Å. The Sm(2)-O(4) bond length is 2.67 Å. The Sm(2)-O(6) bond length is 2.36 Å. The Sm(2)-O(8) bond length is 2.29 Å. In the third Sm site, Sm(3) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(3), one O(4), one O(5), and one O(7) atom. The Sm(3)-O(10) bond length is 2.30 Å. The Sm(3)-O(2) bond length is 2.51 Å. The Sm(3)-O(3) bond length is 2.74 Å. The Sm(3)-O(4) bond length is 2.64 Å. The Sm(3)-O(5) bond length is 2.27 Å. The Sm(3)-O(7) bond length is 2.25 Å. In the fourth Sm site, Sm(4) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(6), one O(8), and one O(9) atom. The Sm(4)-O(1) bond length is 2.50 Å. The Sm(4)-O(2) bond length is 2.46 Å. The Sm(4)-O(3) bond length is 2.40 Å. The Sm(4)-O(4) bond length is 2.66 Å. The Sm(4)-O(6) bond length is 2.32 Å. The Sm(4)-O(8) bond length is 2.30 Å. The Sm(4)-O(9) bond length is 2.64 Å. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), one O(4), and one O(5) atom. The Cu(1)-O(1) bond length is 1.96 Å. The Cu(1)-O(2) bond length is 1.99 Å. The Cu(1)-O(3) bond length is 1.94 Å. The Cu(1)-O(4) bond length is 1.94 Å. The Cu(1)-O(5) bond length is 2.64 Å. In the second Cu site, Cu(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form distorted CuO5 square pyramids that share  a cornercorner with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 44°. The Cu(2)-O(1) bond length is 1.99 Å. The Cu(2)-O(2) bond length is 1.99 Å. The Cu(2)-O(3) bond length is 2.04 Å. The Cu(2)-O(4) bond length is 2.01 Å. The Cu(2)-O(7) bond length is 2.30 Å. In the third Cu site, Cu(3) is bonded to one O(10), one O(5), one O(8), and one O(9) atom to form distorted CuO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 8-42°. The Cu(3)-O(10) bond length is 2.11 Å. The Cu(3)-O(5) bond length is 2.07 Å. The Cu(3)-O(8) bond length is 2.14 Å. The Cu(3)-O(9) bond length is 2.06 Å. In the fourth Cu site, Cu(4) is bonded in a 2-coordinate geometry to one O(10), one O(6), and one O(9) atom. The Cu(4)-O(10) bond length is 2.48 Å. The Cu(4)-O(6) bond length is 1.85 Å. The Cu(4)-O(9) bond length is 1.83 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Sm(1), one Sm(2), one Sm(4), one Cu(1), and one Cu(2) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Sm(1), one Sm(2), one Sm(3), one Sm(4), one Cu(1), and one Cu(2) atom. In the third O site, O(3) is bonded to one Sm(1), one Sm(2), one Sm(3), one Sm(4), one Cu(1), and one Cu(2) atom to form distorted OSm4Cu2 octahedra that share corners with two equivalent O(10)Sm2MgCu2 trigonal bipyramids, corners with two equivalent O(8)Sm2MgCu trigonal pyramids, and faces with two equivalent O(4)Sm4Cu2 octahedra. In the fourth O site, O(4) is bonded to one Sm(1), one Sm(2), one Sm(3), one Sm(4), one Cu(1), and one Cu(2) atom to form distorted OSm4Cu2 octahedra that share corners with two equivalent O(10)Sm2MgCu2 trigonal bipyramids,  an edgeedge with one O(8)Sm2MgCu trigonal pyramid, and faces with two equivalent O(3)Sm4Cu2 octahedra. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Mg(1), one Sm(1), one Sm(3), one Cu(1), and one Cu(3) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Mg(1), one Sm(2), one Sm(4), and one Cu(4) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Mg(1), one Sm(1), one Sm(3), and one Cu(2) atom. In the eighth O site, O(8) is bonded to one Mg(1), one Sm(2), one Sm(4), and one Cu(3) atom to form OSm2MgCu trigonal pyramids that share corners with two equivalent O(3)Sm4Cu2 octahedra,  a cornercorner with one O(10)Sm2MgCu2 trigonal bipyramid,  an edgeedge with one O(4)Sm4Cu2 octahedra, and  an edgeedge with one O(10)Sm2MgCu2 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 57-95°. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one Mg(1), one Sm(1), one Sm(4), one Cu(3), and one Cu(4) atom. In the tenth O site, O(10) is bonded to one Mg(1), one Sm(2), one Sm(3), one Cu(3), and one Cu(4) atom to form distorted OSm2MgCu2 trigonal bipyramids that share corners with two equivalent O(3)Sm4Cu2 octahedra, corners with two equivalent O(4)Sm4Cu2 octahedra,  a cornercorner with one O(8)Sm2MgCu trigonal pyramid, and  an edgeedge with one O(8)Sm2MgCu trigonal pyramid. The corner-sharing octahedral tilt angles range from 16-73°.