Tetrahedra can explain the specificity of water

Researchers at the Institute of Industrial Technology at the University of Tokyo investigated experimental data to show that supercooled water has a liquid-to-liquid phase transition between irregular and tetrahedrally structured forms. They found evidence of a critical issue based on the co-operative structure of the tetrahedron, and its small role in water incompatibilities. This work shows that the special qualities of water – which are essential for life – are mainly produced by the two-state facility.

As we know liquid water is essential for life, however, many of its properties do not correspond to the way other liquids behave. Some of these inconsistencies, such as the maximum density of water at 4 ° C and its large heat capacity, have important implications for living organisms. The origins of these traits have been hotly debated in the scientific community since Rentgen’s time.

Now, researchers at the University of Tokyo have used a two-state model that has the dynamic coexistence of two types of molecular structures in liquid water. This is the familiar disordered normal-fluid structure and locally tetrahedral formation. Like many other phase transitions, there may be a “critical issue” on which the relationship between tetrahedrons takes a power-law form, meaning that there will no longer be a “typical” length scale.

Using computer simulations of water molecules, with extensive analysis of experimental structural, thermodynamic and dynamic data, including X-ray scattering, density, compressibility and viscosity measurements, researchers narrowed down where a critical issue should be. If it exists.

“If the formation of tetrahedral structures in liquid water under these conditions is cooperative, the transition of the liquid phase with the critical point is possible,” says lead author Rui Shi.

The team showed that these temperatures occur around -90 ° C and around 1,700 atmospheric pressures. Experiments in this series are very difficult: because the water is far below its normal freezing, ice crystals form quickly. However, at these very high pressures the samples may remain liquid in the metastable “supercold” state.

“We have seen evidence that the complex issue is real, but its impact on the experimentally accessible field of liquid water is almost negligible as it is far from a critical issue. This means that water inconsistencies come from a two-state facility, not a critique. Says senior writer Hajim Tanaka. Scientists anticipate that the project will lead to the conversion of a long discussion to address another complex issue of water due to the origin of water incompatibilities and lengthy experimental research.