MgSiO3 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, edges with three equivalent Mg(2)O6 octahedra, and  an edgeedge with one Si(2)O4 tetrahedra. In the second Mg site, Mg(2) 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 distorted MgO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with three equivalent Mg(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(5), and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-68°. In the second Si site, Si(2) is bonded to one O(1), one O(3), and two equivalent O(6) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-71°. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), two equivalent Mg(1), and one Si(2) atom to form distorted corner-sharing OMg3Si trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Mg(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(2) and two equivalent Si(1) atoms. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a trigonal non-coplanar geometry to one Mg(2) and two equivalent Si(2) atoms.
MgSiO3 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(2) atoms to form MgO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra, corners with three equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, edges with three equivalent Mg(2)O6 octahedra, and  an edgeedge with one Si(2)O4 tetrahedra. The Mg(1)-O(3) bond length is 2.16 Å. The Mg(1)-O(5) bond length is 2.00 Å. There is one shorter (2.02 Å) and one longer (2.21 Å) Mg(1)-O(1) bond length. There is one shorter (2.07 Å) and one longer (2.15 Å) Mg(1)-O(2) bond length. In the second Mg site, Mg(2) 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 distorted MgO6 octahedra that share corners with four equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with three equivalent Mg(1)O6 octahedra. The Mg(2)-O(1) bond length is 2.05 Å. The Mg(2)-O(2) bond length is 2.25 Å. The Mg(2)-O(3) bond length is 2.04 Å. The Mg(2)-O(4) bond length is 2.45 Å. The Mg(2)-O(5) bond length is 2.08 Å. The Mg(2)-O(6) bond length is 2.45 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(5), and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-68°. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(5) bond length is 1.60 Å. Both Si(1)-O(4) bond lengths are 1.71 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), and two equivalent O(6) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 37-71°. The Si(2)-O(1) bond length is 1.64 Å. The Si(2)-O(3) bond length is 1.62 Å. There is one shorter (1.68 Å) and one longer (1.69 Å) Si(2)-O(6) bond length. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), two equivalent Mg(1), and one Si(2) atom to form distorted corner-sharing OMg3Si trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Mg(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(2) and two equivalent Si(1) atoms. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a trigonal non-coplanar geometry to one Mg(2) and two equivalent Si(2) atoms.