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One reason the group is called the ICE group is because we do a lot of work trying to understand the structure and properties of ice under various conditions, including (but not limited to) ice under high pressures, near surfaces or as nanoparticles. An example of something we investigate is the surface premelting of ice, which is the phenomenon where there exists a thin film of liquid water covering ice surfaces even at temperatures well below freezing. This was first postulated all the way back in 1859 by Michael Faraday yet it is still an active research topic. Another example is understanding the properties of low-dimensional ice. Delicate balancing between forces means it has different properties to the bulk ice, and it is known to form a variety of structures. Examples of low-dimensional ice include confined and interfacial ice, which are ubiquitous in nature and relevant to areas as diverse as cloud microphysics and tribology. Despite their ubiquity, major gaps in the understanding of these structures and their phase transitions still remain.

The formation mechanisms of ice is an area that is also poorly understood. The liquid form of ice, water, can exist  below 0℃, which is known as supercooling. When ice forms at temperatures close to the melting point, it is almost always due to the presence solid impurities that act as nucleating agents and this is called heterogeneous ice nucleation. A comprehensive understanding of the ice nucleation process can have very important effects on our natural world.  For instance atmospheric ice nucleation on aerosols leads to the formation of ice-rich clouds, which prevents too much solar radiation reaching us. Ice formation can also lead to catastrophic consequences for vehicles operating in harsh-weather conditions, with an example being the recent explosion of a SpaceX rocket when attempting connection with an iced anchor upon landing. Our research aims to further our understanding of ice nucleation by implementing a range of computational techniques, from DFT studies of small water clusters and layers at different surfaces, through to large-timescale molecular dynamics simulations where we directly probe the nucleation mechanism. Beyond heterogeneous nucleation, we have also investigated homogeneous nucleation (where foreign particles are absent) as it gives us a more fundamental understanding of the phenomena. Supercooled water exhibits dynamical heterogeneity, with both immobile and mobile regions of molecules present. There exist strong counter arguments for ice preferentially forming in the mobile and immobile regions, and we recently cleared this debate by showing that it occurs in the latter.

 

Related Publications 

Surface premelting of water ice
B Slater, A Michaelides – Nature Reviews Chemistry (2019) 3, 172
Evidence for stable square ice from quantum Monte Carlo
J Chen, A Zen, JG Brandenburg, D Alfè, A Michaelides – Physical Review B (2016) 94, 220102
Two Dimensional Ice from First Principles: Structures and Phase Transitions
J Chen, G Schusteritsch, CJ Pickard, CG Salzmann, A Michaelides – Phys Rev Lett (2016) 116, 025501
Ice is born in low-mobility regions of supercooled liquid water
M Fitzner, GC Sosso, SJ Cox, A Michaelides – Proceedings of the National Academy of Sciences (2019) 116, 2009
Active sites in heterogeneous ice nucleation-the example of K-rich feldspars
A Kiselev, F Bachmann, P Pedevilla, SJ Cox, A Michaelides, D Gerthsen, T Leisner – Science (2016) 355, 367
What makes a good descriptor for heterogeneous ice nucleation on OH-patterned surfaces
P Pedevilla, M Fitzner, A Michaelides – Physical Review B (2017) 96, 115441