October 1, 2022

La Ronge Northerner

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The material in the extreme conditions of extremely high temperatures and pressures turns out to be remarkably simple and universal

The material in the extreme conditions of extremely high temperatures and pressures turns out to be remarkably simple and universal

Credit: Pixabay/CC0 Public Domain

Scientists at Queen Mary University of London have made two discoveries about the behavior of “supercritical matter” – matter at the critical point where the differences between liquids and gases seem to disappear.

While the behavior of matter at reasonably low temperature and pressure was well understood, the picture of matter at high temperature and pressure was unclear. Above the critical point, the differences between liquids and gases seem to disappear, and the supercritical is thought to become hot, dense, and homogeneous.

The researchers believe that there is a new, yet unrevealed, physics of the matter in the supercritical state.

By applying two parameters – Heat capacity And the length at which the waves can propagate in the system, they made two main discoveries. First, they find that there is a constant reflection The point between the two where a substance changes its physical properties – from liquid-like to gas-like. They also find that this inflection point is remarkably close in all of the systems studied, telling us that supercritical matter is intriguingly simple and amenable to new understanding.

In addition to a basic understanding of states of matter and a phase transition diagram, an understanding of supercritical matter has many practical applications; Hydrogen and helium are supercritical in gas giant planets such as Jupiter and Saturn, and thus control their physical properties. In green environmental applications, supercritical fluids It has also proven highly effective in destroying hazardous waste, but engineers increasingly want guidance in theory in order to improve the efficiency of supercritical operations.

Kostya Trachenko, Professor of Physics at Queen Mary University of London, said, “The proven universality of supercritical matter opens the way to a new physically transparent picture of matter in extreme conditions. This is an exciting prospect from a fundamentals point of view. In addition to understanding and predicting supercritical properties in green environment applications. astronomy and other fields.

“This journey is ongoing and is likely to see exciting developments in the future. For example, it calls into question whether a stationary inflection point is related to traditional higher-order phase transitions? Can it be described using current ideas embedded in phase transition theory, or is there a need for To something completely new and different? As we push the boundaries of what is known, we can identify these new exciting questions and start looking for answers.”


The main problem in understanding supercritical matter was that theories of gases, liquids, and solids were not applicable. It remains unclear what physical parameters will reveal the most prominent characteristics of the supercritical state.

Armed with an early understanding of fluids at low temperatures and pressures, the researchers used two parameters to describe a supercritical.

1. The first parameter is a commonly used property: this is the heat capacity that shows how efficiently the system absorbs heat and contains basic information about the system’s degrees of freedom.

2. The second parameter is less common: the length over which the waves can propagate in the system. This length controls the phase space available to the phonons. When this length reaches the smallest possible value and becomes equal to the separation of atoms, something really interesting happens.

The scholars found that in terms of these two parameters, the issue in harsh conditions Higher pressure and temperature become remarkably global.

This universality is twofold. First, the plot of heat amplitude versus wave propagation length has an amazing fixed point of inflection that corresponds to the transition between two physically different supercritical states: a liquid-like and a gas-like state. When crossing this point of reflection, the supercritical substance changes its switch physical properties. The inflection point serves importantly as an unambiguous way to separate the two states—something that has occupied scientists’ minds for some time.

Second, the location of this inflection point is remarkably close in all types of studied systems. This second world differs markedly from all other known transition points. For example, two of these transition points — the triple point where the three states of matter (liquid, gas, and solid) coexist and exist critical point Where the gas-liquid boiling line ends — varies in different systems. On the other hand, the same inflection point in all systems at extreme supercritical conditions tells us that supercritical issue It is intriguingly simple.

Revealing and demonstrating this simplicity is the main finding of the paper, “Double Universality of Transition in super critical conditionPosted in science progress.

Molecular phase boundaries: a “primitive” gas-liquid transition

more information:
Cockrell et al., The dual universality of transition in the supercritical state, science progress (2022). DOI: 10.1126 / sciadv.abq5183. www.science.org/doi/10.1126/sciadv.abq5183

the quote: Matter under extreme conditions of very high temperature and pressure turns out to be remarkably simple and universal (2022, August 12) Retrieved on August 13, 2022 from https://phys.org/news/2022-08-extreme-conditions-high-pressure the heat. html

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