MgSiO3 crystallizes in the orthorhombic Pbcn space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with eight equivalent Si(1)O4 tetrahedra and edges with three equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with three equivalent Mg(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 Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-68°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded to one Mg(1), two equivalent Mg(2), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Si(1) atom.
MgSiO3 crystallizes in the orthorhombic Pbcn space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with eight equivalent Si(1)O4 tetrahedra and edges with three equivalent Mg(2)O6 octahedra. Both Mg(1)-O(1) bond lengths are 2.50 Å. Both Mg(1)-O(2) bond lengths are 2.10 Å. Both Mg(1)-O(3) bond lengths are 1.98 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with three equivalent Mg(1)O6 octahedra. Both Mg(2)-O(3) bond lengths are 2.08 Å. There are two shorter (2.13 Å) and two longer (2.17 Å) Mg(2)-O(2) 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 Mg(2)O6 octahedra, corners with four equivalent Mg(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 43-68°. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.61 Å. There is one shorter (1.68 Å) and one longer (1.69 Å) Si(1)-O(1) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded to one Mg(1), two equivalent Mg(2), and one Si(1) atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Si(1) atom.