Na2Cd3Si3O10 crystallizes in the monoclinic C2/c space group. Na(1) is bonded to one O(1), one O(3), one O(5), and two equivalent O(4) atoms to form NaO5 square pyramids that share  a cornercorner with one Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, corners with four equivalent Cd(1)O5 trigonal bipyramids,  an edgeedge with one Cd(2)O6 octahedra,  an edgeedge with one Na(1)O5 square pyramid, and  an edgeedge with one Si(1)O4 tetrahedra. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to one O(1), one O(4), one O(5), and two equivalent O(2) atoms to form CdO5 trigonal bipyramids that share corners with two equivalent Cd(2)O6 octahedra, corners with four equivalent Na(1)O5 square pyramids,  a cornercorner with one Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, corners with two equivalent Cd(1)O5 trigonal bipyramids, and  an edgeedge with one Cd(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 62-77°. In the second Cd site, Cd(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form CdO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Cd(1)O5 trigonal bipyramids, edges with two equivalent Na(1)O5 square pyramids, edges with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Cd(1)O5 trigonal bipyramids. 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(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Cd(2)O6 octahedra,  a cornercorner with one Na(1)O5 square pyramid,  a cornercorner with one Si(2)O4 tetrahedra, corners with four equivalent Cd(1)O5 trigonal bipyramids,  an edgeedge with one Cd(2)O6 octahedra, and  an edgeedge with one Na(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 53°. In the second Si site, Si(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with six equivalent Na(1)O5 square pyramids, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Cd(1)O5 trigonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Cd(1), one Cd(2), and one Si(1) atom. In the second O site, O(2) is bonded to one Cd(2), two equivalent Cd(1), and one Si(1) atom to form distorted OCd3Si trigonal pyramids that share corners with two equivalent O(4)Na2CdSi tetrahedra and corners with three equivalent O(2)Cd3Si trigonal pyramids. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded to two equivalent Na(1), one Cd(1), and one Si(2) atom to form distorted ONa2CdSi tetrahedra that share  a cornercorner with one O(4)Na2CdSi tetrahedra, corners with two equivalent O(2)Cd3Si trigonal pyramids, and  an edgeedge with one O(4)Na2CdSi tetrahedra. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Cd(1), one Cd(2), and one Si(1) atom.
Na2Cd3Si3O10 crystallizes in the monoclinic C2/c space group. Na(1) is bonded to one O(1), one O(3), one O(5), and two equivalent O(4) atoms to form NaO5 square pyramids that share  a cornercorner with one Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, corners with four equivalent Cd(1)O5 trigonal bipyramids,  an edgeedge with one Cd(2)O6 octahedra,  an edgeedge with one Na(1)O5 square pyramid, and  an edgeedge with one Si(1)O4 tetrahedra. The Na(1)-O(1) bond length is 2.39 Å. The Na(1)-O(3) bond length is 2.53 Å. The Na(1)-O(5) bond length is 2.45 Å. There is one shorter (2.36 Å) and one longer (2.37 Å) Na(1)-O(4) bond length. There are two inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to one O(1), one O(4), one O(5), and two equivalent O(2) atoms to form CdO5 trigonal bipyramids that share corners with two equivalent Cd(2)O6 octahedra, corners with four equivalent Na(1)O5 square pyramids,  a cornercorner with one Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, corners with two equivalent Cd(1)O5 trigonal bipyramids, and  an edgeedge with one Cd(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 62-77°. The Cd(1)-O(1) bond length is 2.38 Å. The Cd(1)-O(4) bond length is 2.27 Å. The Cd(1)-O(5) bond length is 2.26 Å. There is one shorter (2.31 Å) and one longer (2.35 Å) Cd(1)-O(2) bond length. In the second Cd site, Cd(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form CdO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Cd(1)O5 trigonal bipyramids, edges with two equivalent Na(1)O5 square pyramids, edges with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Cd(1)O5 trigonal bipyramids. Both Cd(2)-O(1) bond lengths are 2.25 Å. Both Cd(2)-O(2) bond lengths are 2.44 Å. Both Cd(2)-O(5) bond lengths are 2.40 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(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Cd(2)O6 octahedra,  a cornercorner with one Na(1)O5 square pyramid,  a cornercorner with one Si(2)O4 tetrahedra, corners with four equivalent Cd(1)O5 trigonal bipyramids,  an edgeedge with one Cd(2)O6 octahedra, and  an edgeedge with one Na(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 53°. The Si(1)-O(1) bond length is 1.63 Å. The Si(1)-O(2) bond length is 1.66 Å. The Si(1)-O(3) bond length is 1.68 Å. The Si(1)-O(5) bond length is 1.64 Å. In the second Si site, Si(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with six equivalent Na(1)O5 square pyramids, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Cd(1)O5 trigonal bipyramids. Both Si(2)-O(3) bond lengths are 1.68 Å. Both Si(2)-O(4) bond lengths are 1.63 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Cd(1), one Cd(2), and one Si(1) atom. In the second O site, O(2) is bonded to one Cd(2), two equivalent Cd(1), and one Si(1) atom to form distorted OCd3Si trigonal pyramids that share corners with two equivalent O(4)Na2CdSi tetrahedra and corners with three equivalent O(2)Cd3Si trigonal pyramids. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded to two equivalent Na(1), one Cd(1), and one Si(2) atom to form distorted ONa2CdSi tetrahedra that share  a cornercorner with one O(4)Na2CdSi tetrahedra, corners with two equivalent O(2)Cd3Si trigonal pyramids, and  an edgeedge with one O(4)Na2CdSi tetrahedra. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Cd(1), one Cd(2), and one Si(1) atom.