Na7O5I2 crystallizes in the tetragonal P4/nmm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), four equivalent O(2), and one I(2) atom. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to four equivalent O(2) and two equivalent I(2) atoms. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to one O(1), two equivalent O(2), one I(2), and two equivalent I(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Na(1) and four equivalent Na(3) atoms to form face-sharing ONa5 square pyramids. In the second O site, O(2) is bonded to one Na(1), two equivalent Na(2), and two equivalent Na(3) atoms to form a mixture of face and corner-sharing ONa5 square pyramids. There are two inequivalent I sites. In the first I site, I(1) is bonded in a body-centered cubic geometry to eight equivalent Na(3) atoms. In the second I site, I(2) is bonded in a 9-coordinate geometry to one Na(1), four equivalent Na(2), and four equivalent Na(3) atoms.
Na7O5I2 crystallizes in the tetragonal P4/nmm space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), four equivalent O(2), and one I(2) atom. The Na(1)-O(1) bond length is 2.45 Å. All Na(1)-O(2) bond lengths are 2.18 Å. The Na(1)-I(2) bond length is 3.23 Å. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to four equivalent O(2) and two equivalent I(2) atoms. All Na(2)-O(2) bond lengths are 2.46 Å. Both Na(2)-I(2) bond lengths are 3.47 Å. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to one O(1), two equivalent O(2), one I(2), and two equivalent I(1) atoms. The Na(3)-O(1) bond length is 2.34 Å. Both Na(3)-O(2) bond lengths are 2.42 Å. The Na(3)-I(2) bond length is 3.30 Å. Both Na(3)-I(1) bond lengths are 3.40 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Na(1) and four equivalent Na(3) atoms to form face-sharing ONa5 square pyramids. In the second O site, O(2) is bonded to one Na(1), two equivalent Na(2), and two equivalent Na(3) atoms to form a mixture of face and corner-sharing ONa5 square pyramids. There are two inequivalent I sites. In the first I site, I(1) is bonded in a body-centered cubic geometry to eight equivalent Na(3) atoms. In the second I site, I(2) is bonded in a 9-coordinate geometry to one Na(1), four equivalent Na(2), and four equivalent Na(3) atoms.