Phase transitions without high energy inputs

Supercooled water exhibits a strange phase, flowing more sluggishly than typical liquids but moving more than true solids. That makes it a strong candidate to study the glass transition problem, which seeks to explain how substances transition between their liquid and solid states.

Phase transitions typically require significant energy inputs, often as heat. Quoc Tuan Truong and Victor Teboul found that even at low temperatures, active molecules could spark the transition from supercooled to liquid water without requiring heat. In virtual experiments, a proportion of only 2.5% active molecules led to a phase transition in water.

“We don’t understand, still, why amorphous, non-crystalline solids are not liquids,” said Teboul. To study the solid-liquid phase transition, they chose to experiment with water due to its unique properties. “Water is a very strange liquid,” said Teboul. “We think that if it works in water, it’s everywhere.”

The researchers designed a computer simulation of 2000 water molecules with varying proportions of active molecules. These molecules increased the movement of adjacent molecules in a snowball fashion until the system flowed like a liquid. The team ran the simulation at different temperatures and concentrations, finding that, at 220 Kelvin, a concentration of only 2.5% active molecules was needed to achieve a transition from supercooled to liquid water.

The researchers concluded that achieving phase transitions without large energy inputs may be a universal property of matter. Theoretically, the discovery should make headway on the glass transition problem. Practically, better understanding supercooled water can enable its use for tissue preservation, since cells can expand and break when frozen.

Source: “A facilitation-induced fluidization transition in supercooled water triggered by a few active molecules,” by Quoc Tuan Truong and Victor Teboul, Physics of Fluids (2025). The article can be accessed at https://doi.org/10.1063/5.0301017 .