Na2SiF6 crystallizes in the trigonal P321 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms to form distorted NaF6 octahedra that share corners with two equivalent Si(2)F6 octahedra, corners with six equivalent Na(2)F6 octahedra, and edges with two equivalent Si(1)F6 octahedra. The corner-sharing octahedral tilt angles range from 47-64°. In the second Na site, Na(2) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms to form NaF6 octahedra that share corners with four equivalent Si(1)F6 octahedra, corners with six equivalent Na(1)F6 octahedra, and  an edgeedge with one Si(2)F6 octahedra. The corner-sharing octahedral tilt angles range from 43-64°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to three equivalent F(1) and three equivalent F(2) atoms to form SiF6 octahedra that share corners with six equivalent Na(2)F6 octahedra and edges with three equivalent Na(1)F6 octahedra. The corner-sharing octahedral tilt angles are 43°. In the second Si site, Si(2) is bonded to six equivalent F(3) atoms to form SiF6 octahedra that share corners with six equivalent Na(1)F6 octahedra and edges with three equivalent Na(2)F6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are three inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(2), and one Si(1) atom. In the second F site, F(2) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(2), and one Si(1) atom. In the third F site, F(3) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(2), and one Si(2) atom.
Na2SiF6 crystallizes in the trigonal P321 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms to form distorted NaF6 octahedra that share corners with two equivalent Si(2)F6 octahedra, corners with six equivalent Na(2)F6 octahedra, and edges with two equivalent Si(1)F6 octahedra. The corner-sharing octahedral tilt angles range from 47-64°. Both Na(1)-F(1) bond lengths are 2.27 Å. Both Na(1)-F(2) bond lengths are 2.28 Å. Both Na(1)-F(3) bond lengths are 2.17 Å. In the second Na site, Na(2) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms to form NaF6 octahedra that share corners with four equivalent Si(1)F6 octahedra, corners with six equivalent Na(1)F6 octahedra, and  an edgeedge with one Si(2)F6 octahedra. The corner-sharing octahedral tilt angles range from 43-64°. Both Na(2)-F(1) bond lengths are 2.31 Å. Both Na(2)-F(2) bond lengths are 2.27 Å. Both Na(2)-F(3) bond lengths are 2.37 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to three equivalent F(1) and three equivalent F(2) atoms to form SiF6 octahedra that share corners with six equivalent Na(2)F6 octahedra and edges with three equivalent Na(1)F6 octahedra. The corner-sharing octahedral tilt angles are 43°. All Si(1)-F(1) bond lengths are 1.70 Å. All Si(1)-F(2) bond lengths are 1.70 Å. In the second Si site, Si(2) is bonded to six equivalent F(3) atoms to form SiF6 octahedra that share corners with six equivalent Na(1)F6 octahedra and edges with three equivalent Na(2)F6 octahedra. The corner-sharing octahedral tilt angles are 47°. All Si(2)-F(3) bond lengths are 1.70 Å. There are three inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(2), and one Si(1) atom. In the second F site, F(2) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(2), and one Si(1) atom. In the third F site, F(3) is bonded in a distorted trigonal planar geometry to one Na(1), one Na(2), and one Si(2) atom.