Sc2Ti2O7 crystallizes in the monoclinic C2/m space group. Sc(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form distorted ScO6 pentagonal pyramids that share corners with four equivalent Ti(1)O5 trigonal bipyramids, edges with three equivalent Sc(1)O6 pentagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. Ti(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted TiO5 trigonal bipyramids that share corners with four equivalent Sc(1)O6 pentagonal pyramids,  a cornercorner with one Ti(1)O5 trigonal bipyramid, edges with two equivalent Sc(1)O6 pentagonal pyramids, and  an edgeedge with one Ti(1)O5 trigonal bipyramid. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sc(1) and one Ti(1) atom. In the second O site, O(2) is bonded to two equivalent Sc(1) and two equivalent Ti(1) atoms to form edge-sharing OSc2Ti2 trigonal pyramids. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ti(1) atoms.
Sc2Ti2O7 crystallizes in the monoclinic C2/m space group. Sc(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form distorted ScO6 pentagonal pyramids that share corners with four equivalent Ti(1)O5 trigonal bipyramids, edges with three equivalent Sc(1)O6 pentagonal pyramids, and edges with two equivalent Ti(1)O5 trigonal bipyramids. Both Sc(1)-O(2) bond lengths are 2.17 Å. There are two shorter (2.05 Å) and two longer (2.17 Å) Sc(1)-O(1) bond lengths. Ti(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted TiO5 trigonal bipyramids that share corners with four equivalent Sc(1)O6 pentagonal pyramids,  a cornercorner with one Ti(1)O5 trigonal bipyramid, edges with two equivalent Sc(1)O6 pentagonal pyramids, and  an edgeedge with one Ti(1)O5 trigonal bipyramid. The Ti(1)-O(3) bond length is 1.80 Å. Both Ti(1)-O(1) bond lengths are 1.83 Å. There is one shorter (1.90 Å) and one longer (2.20 Å) Ti(1)-O(2) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Sc(1) and one Ti(1) atom. In the second O site, O(2) is bonded to two equivalent Sc(1) and two equivalent Ti(1) atoms to form edge-sharing OSc2Ti2 trigonal pyramids. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ti(1) atoms.