Lu2Si2O7 crystallizes in the tetragonal P4_12_12 space group. Lu(1) is bonded to two equivalent O(1), two equivalent O(4), and three equivalent O(2) atoms to form distorted LuO7 pentagonal bipyramids that share corners with five equivalent Si(1)O4 tetrahedra, edges with five equivalent Lu(1)O7 pentagonal bipyramids, and  an edgeedge with one Si(1)O4 tetrahedra. 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 five equivalent Lu(1)O7 pentagonal bipyramids,  a cornercorner with one Si(1)O4 tetrahedra, and  an edgeedge with one Lu(1)O7 pentagonal bipyramid. There are four inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Lu(1) and one Si(1) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Lu(1) and one Si(1) atom. In the fourth O site, O(2) is bonded to three equivalent Lu(1) and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLu3Si trigonal pyramids.
Lu2Si2O7 crystallizes in the tetragonal P4_12_12 space group. Lu(1) is bonded to two equivalent O(1), two equivalent O(4), and three equivalent O(2) atoms to form distorted LuO7 pentagonal bipyramids that share corners with five equivalent Si(1)O4 tetrahedra, edges with five equivalent Lu(1)O7 pentagonal bipyramids, and  an edgeedge with one Si(1)O4 tetrahedra. There is one shorter (2.17 Å) and one longer (2.21 Å) Lu(1)-O(1) bond length. There is one shorter (2.13 Å) and one longer (2.30 Å) Lu(1)-O(4) bond length. There are a spread of Lu(1)-O(2) bond distances ranging from 2.20-2.47 Å. 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 five equivalent Lu(1)O7 pentagonal bipyramids,  a cornercorner with one Si(1)O4 tetrahedra, and  an edgeedge with one Lu(1)O7 pentagonal bipyramid. The Si(1)-O(1) bond length is 1.62 Å. The Si(1)-O(2) bond length is 1.66 Å. The Si(1)-O(3) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.62 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Lu(1) and one Si(1) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Lu(1) and one Si(1) atom. In the fourth O site, O(2) is bonded to three equivalent Lu(1) and one Si(1) atom to form a mixture of distorted corner and edge-sharing OLu3Si trigonal pyramids.