Researchers identify state of matter to possess both solid and liquid state

Scientists have identified that under some specific conditions, some of the elements in the periodic table can exhibit the properties of both solid and liquid.

Cryptate of potassium cation
X-ray crystal structure of a potassium ion bound in cryptand[2.2.2]( Credits - Wikimedia Commons)

A team of researchers from the University of Edinburgh, Scotland used latest models of artificial intelligence (AI) to simulate what could happen if the element potassium was subjected to very high amounts of pressure, ranging from 200,000 to 400,000 times of atmospheric pressure along with heat between 400 – 800 Kelvin.

The atoms of potassium like most of the other metals behave in an ordered manner under normal circumstances. But the team of physicists identified that in case of extreme conditions, they get arranged in complex orders, the atomic core lined up in a cylindrical way, arranged in a ‘X’ shape and four chains alongside it.

The two different arrangements are called as the “host-guest structures”, the co-author of the paper, Andreas Hermann told. The resultant substance is the formation of two intertwined and interlinked lattices which is very unusual.

The study has been published in the journal PNAS in this week and it is reported that in these conditions, potassium atoms possessed an arrangement which is called as the chain-melted state where one lattice known as ‘guest’ lattice dissolved to form liquid while the ‘host’ lattice remained as a solid form. On heating this, the guest atoms melt while the atoms belonging to the host lattice remain crystalline.

The reason behind this is that the host lattice possesses a much stronger bond and thus it remains in the solid state. This is why, a larger amount of energy is needed to melt it. On the other hand the ‘guest’ lattice has a much weaker bond, so it dissolves to turn to a liquid. The two structures, ‘host’ and ‘guest’ lattice comprising of 80% and 20% composition are similar to each other on an atomic level. The only difference between them is on their arrangement in the lattice.

When this substance is observed by the human eyes, it would appear as solid block of potassium which is dissolving to liquid as well as forming a solid structure simultaneously. The team described it as a ‘sponge-like’ material which can soak up the liquid. It can be understood as the sponge which soaks itself up, when it is a liquid and then again reforms itself in the solid state. As the host is 80% and the guest is 20%, the material is always in this state.

This was made possible by AI models and then the findings were tested over a large number of theoretical samples. As a result, the machine learning model can also determine the behaviour of the other elements in similar extreme conditions.


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