MgSiO3 crystallizes in the monoclinic C2/c 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 pentagonal pyramids that share corners with two equivalent Mg(2)O4 trigonal pyramids, corners with four equivalent Si(1)O4 trigonal pyramids,  an edgeedge with one Mg(2)O4 trigonal pyramid, and edges with two equivalent Si(1)O4 trigonal pyramids. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form MgO4 trigonal pyramids that share corners with two equivalent Mg(1)O6 pentagonal pyramids, corners with four equivalent Si(1)O4 trigonal pyramids, and  an edgeedge with one Mg(1)O6 pentagonal pyramid. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted SiO4 trigonal pyramids that share corners with two equivalent Mg(1)O6 pentagonal pyramids, corners with two equivalent Mg(2)O4 trigonal pyramids, corners with two equivalent Si(1)O4 trigonal pyramids, and  an edgeedge with one Mg(1)O6 pentagonal pyramid. 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 in a trigonal planar geometry to one Mg(1), one Mg(2), 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(1) atom.
MgSiO3 crystallizes in the monoclinic C2/c 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 pentagonal pyramids that share corners with two equivalent Mg(2)O4 trigonal pyramids, corners with four equivalent Si(1)O4 trigonal pyramids,  an edgeedge with one Mg(2)O4 trigonal pyramid, and edges with two equivalent Si(1)O4 trigonal pyramids. Both Mg(1)-O(1) bond lengths are 2.14 Å. Both Mg(1)-O(2) bond lengths are 2.12 Å. Both Mg(1)-O(3) bond lengths are 2.15 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form MgO4 trigonal pyramids that share corners with two equivalent Mg(1)O6 pentagonal pyramids, corners with four equivalent Si(1)O4 trigonal pyramids, and  an edgeedge with one Mg(1)O6 pentagonal pyramid. Both Mg(2)-O(2) bond lengths are 2.08 Å. Both Mg(2)-O(3) bond lengths are 1.97 Å. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted SiO4 trigonal pyramids that share corners with two equivalent Mg(1)O6 pentagonal pyramids, corners with two equivalent Mg(2)O4 trigonal pyramids, corners with two equivalent Si(1)O4 trigonal pyramids, and  an edgeedge with one Mg(1)O6 pentagonal pyramid. The Si(1)-O(2) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.63 Å. There is one shorter (1.73 Å) and one longer (1.75 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 in a trigonal planar geometry to one Mg(1), one Mg(2), 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(1) atom.