HIO4 crystallizes in the monoclinic C2 space group. H(1) is bonded in a linear geometry to one O(3) and one O(4) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one I(1) and one I(2) atom. In the second O site, O(2) is bonded in a water-like geometry to one I(1) and one I(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one H(1) and one I(2) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one H(1) and one I(1) atom. There are two inequivalent I sites. In the first I site, I(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted edge-sharing IO6 octahedra. In the second I site, I(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form edge-sharing IO6 octahedra.
HIO4 crystallizes in the monoclinic C2 space group. H(1) is bonded in a linear geometry to one O(3) and one O(4) atom. The H(1)-O(3) bond length is 1.05 Å. The H(1)-O(4) bond length is 1.51 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one I(1) and one I(2) atom. The O(1)-I(1) bond length is 2.00 Å. The O(1)-I(2) bond length is 1.99 Å. In the second O site, O(2) is bonded in a water-like geometry to one I(1) and one I(2) atom. The O(2)-I(1) bond length is 2.08 Å. The O(2)-I(2) bond length is 1.94 Å. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one H(1) and one I(2) atom. The O(3)-I(2) bond length is 1.87 Å. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one H(1) and one I(1) atom. The O(4)-I(1) bond length is 1.80 Å. There are two inequivalent I sites. In the first I site, I(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted edge-sharing IO6 octahedra. In the second I site, I(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form edge-sharing IO6 octahedra.