More evidence that water can change from a liquid to a denser liquid

Aug. 19 () –

New evidence constitutes an important step forward in confirming the idea that water can change from a liquid form to a denser one, first put forward in 1992.

Because the transition has been predicted to occur under supercooled conditions, confirming its existence has been challenging in recent decades. That’s because at these low temperatures, water doesn’t really want to be a liquid, it wants to quickly turn to ice. Due to its hidden status, much is still unknown about this liquid-liquid phase transition, unlike everyday examples of phase transitions in water between a solid or vapor phase and a liquid phase.

The University of Birmingham-led team has used computer simulations to help explain what characteristics distinguish the two liquids at the microscopic level.

As published by Nature Physics, found that the water molecules in the high-density liquid form arrangements that are considered “topologically complex,” such as a trefoil knot or a Hopf bond (similar to two links in a steel chain). Therefore, the molecules in the high-density liquid are said to be entangled.

In contrast, the molecules in the low-density liquid mostly form simple rings, and therefore the molecules in the low-density liquid are not entangled.

The researchers used a colloidal model of water in their simulation, and then two widely used molecular models of water. Colloids are particles that can be a thousand times larger than a single water molecule. By virtue of their relatively larger size and thus slower-moving, colloids are used to observe and understand physical phenomena that also occur on much smaller atomic and molecular length scales.

Dr. Dwaipayan Chakrabarti, a co-author, says it’s a statement: “This colloidal model of water provides a magnifying glass on molecular water and allows us to unravel the secrets of water related to the history of two liquids”.

Professor Sciortino says: “In this work, we propose, for the first time, a view of the liquid-liquid phase transition based on network entanglement ideas. I am sure that this work will inspire new theoretical models based on topological concepts.”

The team hopes that the model they have devised will pave the way for further experiments to validate the theory. and extend the concept of “intertwined” liquids to other liquids.