Li2MgCu2(SiO3)4 crystallizes in the triclinic P-1 space group. Li(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), and two equivalent O(6) atoms. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with four equivalent Cu(1)O5 square pyramids. Cu(1) is bonded to one O(1), one O(3), one O(5), and two equivalent O(2) atoms to form distorted CuO5 square pyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, and  an edgeedge with one Cu(1)O5 square pyramid. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Cu(1)O5 square pyramids, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Cu(1)O5 square pyramids, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-52°. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Mg(1), one Cu(1), and one Si(1) atom to form corner-sharing OLiMgCuSi tetrahedra. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Cu(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Li(1), one Cu(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Li(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Li(1), one Si(1), and one Si(2) atom.
Li2MgCu2(SiO3)4 crystallizes in the triclinic P-1 space group. Li(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), and two equivalent O(6) atoms. The Li(1)-O(1) bond length is 1.97 Å. The Li(1)-O(3) bond length is 2.02 Å. The Li(1)-O(4) bond length is 2.45 Å. There is one shorter (2.20 Å) and one longer (2.44 Å) Li(1)-O(6) bond length. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with four equivalent Cu(1)O5 square pyramids. Both Mg(1)-O(1) bond lengths are 2.04 Å. Both Mg(1)-O(2) bond lengths are 2.04 Å. Both Mg(1)-O(5) bond lengths are 2.25 Å. Cu(1) is bonded to one O(1), one O(3), one O(5), and two equivalent O(2) atoms to form distorted CuO5 square pyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, and  an edgeedge with one Cu(1)O5 square pyramid. The Cu(1)-O(1) bond length is 1.99 Å. The Cu(1)-O(3) bond length is 1.96 Å. The Cu(1)-O(5) bond length is 1.96 Å. There is one shorter (2.01 Å) and one longer (2.48 Å) Cu(1)-O(2) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Cu(1)O5 square pyramids, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.61 Å. The Si(1)-O(4) bond length is 1.65 Å. The Si(1)-O(6) bond length is 1.68 Å. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Cu(1)O5 square pyramids, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-52°. The Si(2)-O(2) bond length is 1.62 Å. The Si(2)-O(4) bond length is 1.67 Å. The Si(2)-O(5) bond length is 1.62 Å. The Si(2)-O(6) bond length is 1.68 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Mg(1), one Cu(1), and one Si(1) atom to form corner-sharing OLiMgCuSi tetrahedra. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Cu(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Li(1), one Cu(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Li(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Li(1), one Si(1), and one Si(2) atom.