Na2SiCBiO7 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 Bi(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 Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 63-81°. 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 Bi(1)O6 octahedra and corners with six equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-69°. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. Bi(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 BiO6 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 63-81°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1), one C(1), and one Bi(1) atom. In the third O site, O(3) is bonded to two equivalent Na(1), one C(1), and one Bi(1) atom to form distorted corner-sharing ONa2BiC trigonal pyramids. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Bi(1) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1), one Si(1), and one Bi(1) atom. In the sixth O site, O(6) is bonded to two equivalent Na(1), one Si(1), and one Bi(1) atom to form distorted corner-sharing ONa2SiBi tetrahedra.
Na2SiCBiO7 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 Bi(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 Bi(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 63-81°. The Na(1)-O(1) bond length is 2.25 Å. The Na(1)-O(2) bond length is 2.47 Å. The Na(1)-O(3) bond length is 2.49 Å. The Na(1)-O(4) bond length is 2.46 Å. The Na(1)-O(5) bond length is 2.54 Å. The Na(1)-O(6) bond length is 2.60 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 Bi(1)O6 octahedra and corners with six equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-69°. The Si(1)-O(5) bond length is 1.66 Å. The Si(1)-O(6) bond length is 1.65 Å. Both Si(1)-O(4) bond lengths are 1.65 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 1.32 Å. The C(1)-O(3) bond length is 1.33 Å. Bi(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 BiO6 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 63-81°. The Bi(1)-O(2) bond length is 2.33 Å. The Bi(1)-O(3) bond length is 2.38 Å. The Bi(1)-O(5) bond length is 2.24 Å. The Bi(1)-O(6) bond length is 2.31 Å. Both Bi(1)-O(4) bond lengths are 2.23 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one C(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1), one C(1), and one Bi(1) atom. In the third O site, O(3) is bonded to two equivalent Na(1), one C(1), and one Bi(1) atom to form distorted corner-sharing ONa2BiC trigonal pyramids. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Bi(1) atom. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1), one Si(1), and one Bi(1) atom. In the sixth O site, O(6) is bonded to two equivalent Na(1), one Si(1), and one Bi(1) atom to form distorted corner-sharing ONa2SiBi tetrahedra.