Na2SiCSbO7 crystallizes in the monoclinic P2_1/m space group. Na(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Na(1)O6 octahedra,  a faceface with one Na(1)O6 octahedra, and  a faceface with one Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 61-83°. Si(1) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with four equivalent Sb(1)O6 octahedra and corners with six equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-74°. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. Sb(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form distorted SbO6 octahedra that share corners with four equivalent Na(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, and faces with two equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 61-83°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one C(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Na(1), one C(1), and one Sb(1) atom. In the third O site, O(3) is bonded in a distorted trigonal pyramidal geometry to two equivalent Na(1), one C(1), and one Sb(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Sb(1) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to two equivalent Na(1), one Si(1), and one Sb(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Si(1), and one Sb(1) atom.
Na2SiCSbO7 crystallizes in the monoclinic P2_1/m space group. Na(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with three equivalent Si(1)O4 tetrahedra,  an edgeedge with one Na(1)O6 octahedra,  a faceface with one Na(1)O6 octahedra, and  a faceface with one Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 61-83°. The Na(1)-O(1) bond length is 2.25 Å. The Na(1)-O(2) bond length is 2.45 Å. The Na(1)-O(3) bond length is 2.45 Å. The Na(1)-O(4) bond length is 2.52 Å. The Na(1)-O(5) bond length is 2.49 Å. The Na(1)-O(6) bond length is 2.64 Å. Si(1) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with four equivalent Sb(1)O6 octahedra and corners with six equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-74°. The Si(1)-O(5) bond length is 1.67 Å. The Si(1)-O(6) bond length is 1.66 Å. Both Si(1)-O(4) bond lengths are 1.64 Å. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. The C(1)-O(1) bond length is 1.25 Å. The C(1)-O(2) bond length is 1.33 Å. The C(1)-O(3) bond length is 1.32 Å. Sb(1) is bonded to one O(2), one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form distorted SbO6 octahedra that share corners with four equivalent Na(1)O6 octahedra, corners with four equivalent Si(1)O4 tetrahedra, and faces with two equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 61-83°. The Sb(1)-O(2) bond length is 2.19 Å. The Sb(1)-O(3) bond length is 2.33 Å. The Sb(1)-O(5) bond length is 2.08 Å. The Sb(1)-O(6) bond length is 2.21 Å. Both Sb(1)-O(4) bond lengths are 2.10 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one C(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Na(1), one C(1), and one Sb(1) atom. In the third O site, O(3) is bonded in a distorted trigonal pyramidal geometry to two equivalent Na(1), one C(1), and one Sb(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Sb(1) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to two equivalent Na(1), one Si(1), and one Sb(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Si(1), and one Sb(1) atom.