Polymorphism of H/D-Sublattices in Water Ice

This project revolves about ice crystals. Most of us know the beauty of frozen lakes, snowcrystals in winter or ice cubes to keep your drink cold. A snowflake, no matter whether it is generated in the lab or formed in nature in clouds, always features a high symmetry and six identical arms. Yet, when looking at molecular length scales, when looking at how H2O molecules are connected, the ice crystal is by no means perfect. In physical chemistry regular ice is called hexagonal ice (ice Ih) because oft he siixfold symmetry. Yet it is also called a frustrated crystal, because it is only partially symmetric. When looking at the H-atoms and O-atoms alone, we find a perfect six-fold symmetry for O-atoms, but we find H-atoms at more or less random positions. This means that every single water molecule points in a different direction and features disorder. In this project we will investigate on methods how to produce a perfect, fully ordered crystal in which also all H-atoms are at position that are well defined through symmetry. This is called the fully ordered ice and only exists at very low temperatures in case of regular ice at temperatures below -200C. Such kind of ice was discoverd only in the 1970 and is now known as ice XI. This kind of transition from a disordered ice crystal to an ordered ice crystal upon cooling is not only known for the ice that we find commonly on Earth. It is also found for more exotic kinds of ice that are found in space, e.g., in the interior of the icy moons of Jupiter and Saturn or deep inside the ice giants Uranus and Neptune. Such ices are referred to as high-pressure ices, where at the moment in total nineteen different types of ice, named from ice I to ice XIX, can be made in the laboratory. Ice XIX was in fact discovered only a few years ago simultaneously by Prof. Komatsu at the U Tokyo and Prof. Loerting at the U Innsbruck, who now collaborate on the present project. These exotic ice forms have very special properties: some of them are like metals, others do not melt up to temperatures of +1000C and they feature very different types of symmetry, from monoclinic to cubic. In this project we are searching to understand the order-disorder transition for high-pressure ices and to understand how fast the ordering takes place, how defects in the ice lattice accelerate the ordering. Possibly this research will allow us to discover unknown ices in the laboratory. We will then record infrared spectra and characterize the ices in terms of crystal structure, density and many more properties. Especially the spectroscopic data for the ices will be of high-relevance to understand the types of ices found in space, e.g., the icy polar caps of Mars, the ices on the Saturn rings, the ices on interstellar dust clouds or the ices on icy moons, icy planets. This will allow space agencies to identify the spectral signatures they observe through space telescopes such as the James- Webb-Space-Telescope (JWST). Our laboratory data will also be of relevance to understand so-called ice quakes, seismic events triggered by ice VI and ice VII in the interior of Earth, and to understand the conversions of ice that take place in cryo-volcanoes in our solar system, i.e., volcanoes that eject water/ice into space instead of lava into the atmosphere.