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(2), one O(3), one O(5), and two equivalent O(6) atoms to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Si(2)O4 trigonal pyramids, and  an edgeedge with one Si(2)O4 trigonal pyramid. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(6) atom. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Mg(1)O5 trigonal bipyramids and corners with two equivalent Si(2)O4 trigonal pyramids. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form distorted SiO4 trigonal pyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. There are six inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mg(2) and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1), one Mg(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(2), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a trigonal non-coplanar geometry to one Mg(1), one Mg(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(2) atom.
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(2), one O(3), one O(5), and two equivalent O(6) atoms to form distorted MgO5 trigonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Si(2)O4 trigonal pyramids, and  an edgeedge with one Si(2)O4 trigonal pyramid. The Mg(1)-O(2) bond length is 2.24 Å. The Mg(1)-O(3) bond length is 1.96 Å. The Mg(1)-O(5) bond length is 2.01 Å. There is one shorter (2.02 Å) and one longer (2.06 Å) Mg(1)-O(6) bond length. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(6) atom. The Mg(2)-O(1) bond length is 1.89 Å. The Mg(2)-O(3) bond length is 2.14 Å. The Mg(2)-O(4) bond length is 2.33 Å. The Mg(2)-O(5) bond length is 2.03 Å. The Mg(2)-O(6) bond length is 2.29 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Mg(1)O5 trigonal bipyramids and corners with two equivalent Si(2)O4 trigonal pyramids. The Si(1)-O(1) bond length is 1.58 Å. The Si(1)-O(2) bond length is 1.68 Å. The Si(1)-O(3) bond length is 1.63 Å. The Si(1)-O(4) bond length is 1.78 Å. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form distorted SiO4 trigonal pyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The Si(2)-O(2) bond length is 1.68 Å. The Si(2)-O(4) bond length is 1.66 Å. The Si(2)-O(5) bond length is 1.62 Å. The Si(2)-O(6) bond length is 1.70 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mg(2) and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a T-shaped geometry to one Mg(1), one Mg(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Mg(2), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a trigonal non-coplanar geometry to one Mg(1), one Mg(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Mg(2), two equivalent Mg(1), and one Si(2) atom.