assoz. Prof. Dr. Thomas Loerting
Cryochemistry of Water
Our group deals with water and aqueous solutions below the freezing point, in particular with crystalline ice, amorphous ice, deeply supercooled liquid water and clathrate hydrates. Highlights in basic research include the discovery of a third amorphous ice (VHDA) and a crystalline ice form (Ice XIX). In applied research, we are developing reference data for the spectroscopic discovery of twenty different ice forms in space and are working on the friction of luge runners on ice at the interface between science and high-performance sport.
At the basic research level, we are interested in understanding the properties that make water so unique and the molecule without which life is impossible. At the center of interest is the idea that liquid water as we know it is actually a mixture of two different liquids (HDL and LDL). At very low temperatures and under pressure, we are able to separate and isolate these two. We study the physical and chemical properties of HDL and LDL individually, such as density and heat capacity, or how they differ in terms of solubility or chemical reactivity.
We investigate the various forms of frozen water, such as in the interior of the Earth, in the interior of icy moons, on Saturn's rings or covering interstellar dust. There are 20 different crystalline forms of ice, plus three different non-crystalline, amorphous forms of ice. Two of these, ice XIX and VHDA, were discovered in our research group. Some of them, such as LDA or ice Ih, are ubiquitous in space. We know ice VI and ice VII from diamond inclusions from the interior of the Earth. Other forms are still undiscovered in nature - but temperature and pressure conditions suggest that some could be present on icy moons of Jupiter or Saturn, for example. We therefore support space missions such as JUICE or space telescopes such as the JWST by providing reference data, for example in the field of infrared and Raman spectroscopy.
Ice formation in a KCl solution
At the applied research level, we deal with the freezing and thawing of aqueous solutions. Freeze concentration and uncontrolled crystallization during thawing can damage cells or drug substances. We clarify which chemical processes take place during freezing and thawing and which phenomena lead to damage. These include vitrification, clathrate formation, the formation of a network of veins containing freeze-concentrated solution, crystallization during freezing and cold crystallization during thawing. These processes change the pH values of the solution or lead to the aggregation of proteins.
Clathrate hydrates are ice-like inclusion compounds that are characterized by the inclusion of mostly apolar molecules in ice cages. Methane clathrates are found in huge quantities in permafrost and on the coastal ocean floor. They are energy-relevant, for example for the transportation of methane/natural gas in pipelines or for hydrogen storage. They are also relevant to the climate - as the sudden decay of methane clathrates represents a climate tipping point that would trigger massive global warming (“clathrate gun”). We focus on the different cages and crystal structures, as well as the factors that control the formation, stability and decay of clathrate hydrates, in particular the elucidation of the phenomenon of anomalous self-preservation.