New study proves that water separates into two different liquids at low temperatures

“This colloidal model of water provides a magnifying glass into molecular water, and enables us to unravel the secrets of water concerning the tale of two liquids,” said Chakrabarti.

The team anticipates that the model they have created will open the door for novel research that will support the theory and broaden the definition of “entangled” liquids to include other liquids like silicon.

“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 this work will inspire novel theoretical modeling based on topological concepts,” says Francesco Sciortino, who was a member of the original research group at Boston University in Massachusetts and now is a professor at Sapienza Università di Roma.

The results of the research were published in the journal Nature Physics.

Abstract:

The first-order phase transition between two tetrahedral networks of different density—introduced as a hypothesis to account for the anomalous behaviour of certain thermodynamic properties of deeply supercooled water—has received strong support from a growing body of work in recent years. Here we show that this liquid–liquid phase transition in tetrahedral networks can be described as a transition between an unentangled, low-density liquid and an entangled, high-density liquid, the latter containing an ensemble of topologically complex motifs. We first reveal this distinction in a rationally designed colloidal analogue of water. We show that this colloidal water model displays the well-known water thermodynamic anomalies as well as a liquid–liquid critical point. We then investigate water, employing two widely used molecular models, to demonstrate that there is also a clear topological distinction between its two supercooled liquid networks, thereby establishing the generality of this observation, which might have far-reaching implications for understanding liquid–liquid phase transitions in tetrahedral liquids.

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