Ca2Nd3Si3O13 crystallizes in the hexagonal P6_3/m space group. Ca(1) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(2), and three equivalent O(3) atoms. Nd(1) is bonded to one O(1), one O(3), one O(4), and four equivalent O(2) atoms to form distorted NdO7 pentagonal bipyramids that share corners with six equivalent Nd(1)O7 pentagonal bipyramids, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with four equivalent Nd(1)O7 pentagonal bipyramids and  an edgeedge with one Nd(1)O7 pentagonal bipyramid. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Nd(1), and one Si(1) atom. In the second O site, O(4) is bonded in a trigonal planar geometry to three equivalent Nd(1) atoms. In the third O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Nd(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a 1-coordinate geometry to one Ca(1), two equivalent Nd(1), and one Si(1) atom.
Ca2Nd3Si3O13 crystallizes in the hexagonal P6_3/m space group. Ca(1) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(2), and three equivalent O(3) atoms. All Ca(1)-O(1) bond lengths are 2.52 Å. All Ca(1)-O(2) bond lengths are 2.89 Å. All Ca(1)-O(3) bond lengths are 2.43 Å. Nd(1) is bonded to one O(1), one O(3), one O(4), and four equivalent O(2) atoms to form distorted NdO7 pentagonal bipyramids that share corners with six equivalent Nd(1)O7 pentagonal bipyramids, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Si(1)O4 tetrahedra. The Nd(1)-O(1) bond length is 2.41 Å. The Nd(1)-O(3) bond length is 2.65 Å. The Nd(1)-O(4) bond length is 2.37 Å. There are two shorter (2.38 Å) and two longer (2.53 Å) Nd(1)-O(2) bond lengths. Si(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with four equivalent Nd(1)O7 pentagonal bipyramids and  an edgeedge with one Nd(1)O7 pentagonal bipyramid. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.63 Å. Both Si(1)-O(2) bond lengths are 1.65 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Nd(1), and one Si(1) atom. In the second O site, O(4) is bonded in a trigonal planar geometry to three equivalent Nd(1) atoms. In the third O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Nd(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a 1-coordinate geometry to one Ca(1), two equivalent Nd(1), and one Si(1) atom.