What is it about?

Water can stay liquid for some time below the freezing point, a phenomenon known as supercooling. In the supercooled state, water has shown remarkable properties, including separating into two different liquids: high-density and low-density water. However, the colder water becomes, the faster it freezes, making it hard to investigate the deeply supercooled regime with experiments. Our simulations allowed us to bypass this problem and confirm the unexpected increase in the surface tension of supercooled water (a so-called inflection point) and to link its origin to the accumulation of high-density water at its surface, showing that the surface of supercooled water is unexpectedly inhomogeneous.

Featured Image

Why is it important?

Detailed knowledge of the properties of supercooled water is critical for climate modelling because water droplets in the atmosphere can reach the supercooled regime. Another area where this information could prove helpful is the study of microorganism cold adaptation and cell cryopreservation.


Supercooled water shows a number of unexpected properties and has never stopped providing scientists with new and interesting phenomena. The supercooled water surface is an even more complex and surprising environment. This research opens the way to investigating liquid/liquid phase separation at the free surface of water, leaving the question open of whether a second-order phase transition is present and how freezing proceeds in the presence of a free surface.

Marcello Sega

Read the Original

This page is a summary of: High-density liquid (HDL) adsorption at the supercooled water/vapor interface and its possible relation to the second surface tension inflection point, The Journal of Chemical Physics, February 2023, American Institute of Physics, DOI: 10.1063/5.0132985.
You can read the full text:



The following have contributed to this page