University of Edinburgh. School of Physics and Astronomy. Institute of Condensed Matter and Complex Systems.. (2015). Pressure-induced localisation of the hydrogen-bond network in KOH-VI, [dataset]. http://dx.doi.org/10.7488/ds/392.
Using a combination of ab initio crystal structure prediction and neutron diffraction techniques,
we have solved the full structure of KOH-VI at 7 GPa. Rather than being orthorhombic and
proton-ordered as had previously be proposed we find that this high-pressure phase of potassium
hydroxide is tetragonal (space group I4/mmm) and proton disordered. It has an unusual hydrogen
bond topology, where the hydroxyl groups form isolated hydrogen-bonded square planar (OH)4
units. This structure is stable above 6.5 GPa and, despite being macroscopically proton-disordered,
local ice rules enforce microscopic order of the hydrogen bonds. We suggest the use of this novel
type of structure to study concerted proton tunneling in the solid state, while the topology of the
hydrogen bond network could conceivably be exploited in data storage applications based solely on
the manipulations of hydrogen bonds. The unusual localisation of the hydrogen bond network under
applied pressure is found to be favored by a more compact packing of the constituents in a distorted
cesium chloride lattice.