Mg2SiO4 is Ilmenite-like structured and crystallizes in the monoclinic P2/m space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form MgO6 octahedra that share corners with two equivalent Mg(3)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Mg(4)O6 octahedra,  an edgeedge with one Mg(5)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra,  an edgeedge with one Si(1)O4 tetrahedra, and  an edgeedge with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 56-57°. In the second Mg site, Mg(2) is bonded to two equivalent O(5) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent Mg(3)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. In the third Mg site, Mg(3) is bonded to two equivalent O(6) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent Mg(2)O6 octahedra, corners with eight equivalent Mg(1)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with four equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-57°. In the fourth Mg site, Mg(4) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(5)O6 octahedra, and edges with four equivalent Mg(1)O6 octahedra. In the fifth Mg site, Mg(5) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(4)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with two equivalent Si(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(6), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(3)O6 octahedra,  a cornercorner with one Mg(5)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(4)O6 octahedra,  an edgeedge with one Mg(5)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-55°. In the second Si site, Si(2) is bonded to one O(3), one O(5), and two equivalent O(4) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(4)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(3)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-56°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(4), one Mg(5), and one Si(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(5), two equivalent Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(4), two equivalent Mg(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Mg(3), and one Si(2) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Mg(3), two equivalent Mg(1), and one Si(1) atom.
Mg2SiO4 is Ilmenite-like structured and crystallizes in the monoclinic P2/m space group. There are five inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form MgO6 octahedra that share corners with two equivalent Mg(3)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Mg(4)O6 octahedra,  an edgeedge with one Mg(5)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra,  an edgeedge with one Si(1)O4 tetrahedra, and  an edgeedge with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 56-57°. The Mg(1)-O(1) bond length is 2.07 Å. The Mg(1)-O(2) bond length is 2.14 Å. The Mg(1)-O(3) bond length is 2.07 Å. The Mg(1)-O(4) bond length is 2.05 Å. The Mg(1)-O(5) bond length is 2.11 Å. The Mg(1)-O(6) bond length is 2.06 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(5) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent Mg(3)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. Both Mg(2)-O(5) bond lengths are 2.10 Å. All Mg(2)-O(4) bond lengths are 2.10 Å. In the third Mg site, Mg(3) is bonded to two equivalent O(6) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with four equivalent Mg(2)O6 octahedra, corners with eight equivalent Mg(1)O6 octahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with four equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 55-57°. Both Mg(3)-O(6) bond lengths are 2.24 Å. All Mg(3)-O(4) bond lengths are 2.26 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(5)O6 octahedra, and edges with four equivalent Mg(1)O6 octahedra. Both Mg(4)-O(3) bond lengths are 2.33 Å. All Mg(4)-O(1) bond lengths are 2.32 Å. In the fifth Mg site, Mg(5) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(4)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with two equivalent Si(1)O4 tetrahedra. Both Mg(5)-O(2) bond lengths are 2.13 Å. All Mg(5)-O(1) bond lengths are 2.02 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(6), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(3)O6 octahedra,  a cornercorner with one Mg(5)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(4)O6 octahedra,  an edgeedge with one Mg(5)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 2-55°. The Si(1)-O(2) bond length is 1.62 Å. The Si(1)-O(6) bond length is 1.68 Å. Both Si(1)-O(1) bond lengths are 1.69 Å. In the second Si site, Si(2) is bonded to one O(3), one O(5), and two equivalent O(4) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(4)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(3)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-56°. The Si(2)-O(3) bond length is 1.68 Å. The Si(2)-O(5) bond length is 1.62 Å. Both Si(2)-O(4) bond lengths are 1.68 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(4), one Mg(5), and one Si(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(5), two equivalent Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Mg(4), two equivalent Mg(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mg(2), one Mg(3), and one Si(2) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Mg(3), two equivalent Mg(1), and one Si(1) atom.