MgSiO3 crystallizes in the monoclinic P2/c space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(5) 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(1)O6 octahedra, and edges with three equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(6) atoms to form distorted MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with three equivalent Mg(1)O6 octahedra, and edges with two equivalent Si(2)O4 tetrahedra. In the third Mg site, Mg(3) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, edges with two equivalent Mg(3)O6 octahedra, and edges with three equivalent Mg(4)O6 octahedra. In the fourth Mg site, Mg(4) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with six equivalent Si(1)O4 tetrahedra, and edges with three equivalent Mg(3)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(3)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Mg(4)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-75°. In the second Si site, Si(2) is bonded to one O(4), one O(5), and two equivalent O(6) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(4)O6 octahedra, corners with two equivalent Mg(3)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-61°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a T-shaped geometry to one Mg(1), one Mg(2), and one Si(2) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to one Mg(2) and two equivalent Si(2) atoms. In the third O site, O(1) is bonded to one Mg(2), two equivalent Mg(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(3), one Mg(4), and one Si(1) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mg(4) and two equivalent Si(1) atoms. In the sixth O site, O(4) is bonded to one Mg(4), two equivalent Mg(3), and one Si(2) atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids.
MgSiO3 crystallizes in the monoclinic P2/c space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(5) 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(1)O6 octahedra, and edges with three equivalent Mg(2)O6 octahedra. Both Mg(1)-O(5) bond lengths are 2.04 Å. There are two shorter (2.10 Å) and two longer (2.21 Å) Mg(1)-O(1) bond lengths. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(6) atoms to form distorted MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with three equivalent Mg(1)O6 octahedra, and edges with two equivalent Si(2)O4 tetrahedra. Both Mg(2)-O(1) bond lengths are 2.07 Å. Both Mg(2)-O(5) bond lengths are 2.04 Å. Both Mg(2)-O(6) bond lengths are 2.27 Å. In the third Mg site, Mg(3) is bonded to two equivalent O(2) and four equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, edges with two equivalent Mg(3)O6 octahedra, and edges with three equivalent Mg(4)O6 octahedra. Both Mg(3)-O(2) bond lengths are 2.07 Å. There are two shorter (2.09 Å) and two longer (2.19 Å) Mg(3)-O(4) bond lengths. In the fourth Mg site, Mg(4) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with six equivalent Si(1)O4 tetrahedra, and edges with three equivalent Mg(3)O6 octahedra. Both Mg(4)-O(2) bond lengths are 2.02 Å. Both Mg(4)-O(3) bond lengths are 2.66 Å. Both Mg(4)-O(4) bond lengths are 2.07 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(3)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Mg(4)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-75°. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(2) bond length is 1.62 Å. There is one shorter (1.68 Å) and one longer (1.69 Å) Si(1)-O(3) bond length. In the second Si site, Si(2) is bonded to one O(4), one O(5), and two equivalent O(6) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Mg(4)O6 octahedra, corners with two equivalent Mg(3)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-61°. The Si(2)-O(4) bond length is 1.64 Å. The Si(2)-O(5) bond length is 1.60 Å. There is one shorter (1.67 Å) and one longer (1.68 Å) Si(2)-O(6) bond length. There are six inequivalent O sites. In the first O site, O(5) is bonded in a T-shaped geometry to one Mg(1), one Mg(2), and one Si(2) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to one Mg(2) and two equivalent Si(2) atoms. In the third O site, O(1) is bonded to one Mg(2), two equivalent Mg(1), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(3), one Mg(4), and one Si(1) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mg(4) and two equivalent Si(1) atoms. In the sixth O site, O(4) is bonded to one Mg(4), two equivalent Mg(3), and one Si(2) atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids.