MgCu(SiO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Mg(1) is bonded in a see-saw-like geometry to two equivalent O(2) and two equivalent O(3) atoms. Cu(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form distorted CuO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Cu(1)O6 octahedra. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Cu(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-65°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Cu(1), and one Si(1) atom.
MgCu(SiO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Mg(1) is bonded in a see-saw-like geometry to two equivalent O(2) and two equivalent O(3) atoms. Both Mg(1)-O(2) bond lengths are 1.97 Å. Both Mg(1)-O(3) bond lengths are 2.03 Å. Cu(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form distorted CuO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Cu(1)O6 octahedra. Both Cu(1)-O(2) bond lengths are 2.13 Å. There are two shorter (1.94 Å) and two longer (2.44 Å) Cu(1)-O(3) bond lengths. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Cu(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-65°. The Si(1)-O(2) bond length is 1.61 Å. The Si(1)-O(3) bond length is 1.65 Å. There is one shorter (1.65 Å) and one longer (1.66 Å) Si(1)-O(1) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Cu(1), and one Si(1) atom.