Support Ukraine’s Army
Youtube
Facebook
The fourth state of water is real, scientists say
For the first time in history, scientists at the University of Vienna have recorded the rare "hexatic" phase of matter, which occurs when atomically thin crystals melt. These findings resolve long-standing debates about the behavior of ultrathin materials when heated.
This topic is discussed in a study published in Science.
How do two-dimensional crystals melt, and what is a "hexatic" phase?
Under normal conditions, ice melts into water at a certain temperature without "stopping" between states. However, two-dimensional materials can undergo a transitional phase. In this state, the atoms are arranged chaotically, as in a liquid, but the angles between the particles remain ordered, which is a property characteristic of solid bodies.
To observe this phenomenon, researchers created a "sandwich"-shaped sample: They placed a layer of silver iodide between two sheets of graphene. They heated the sample with a special holder to a temperature above 1,100°C (2012°F) and observed the process through a scanning transmission electron microscope (STEM), which allows one to distinguish individual atoms.
The amount of information obtained during the recording was so large that artificial intelligence was necessary for the analysis. They trained a neural network to track the movement of thousands of atoms in real time. This allowed them to thoroughly analyze how the material's structure changes during heating.
The analysis revealed that at around 25°C below the complete melting point, the crystal transitions to a hexatic phase, exhibiting "mixed" properties. However, the results diverged from 1970s theories that assumed all transitions in such materials should be gradual. In reality, only the transition from the solid state to the intermediate state was smooth. The transition from the hexatic phase to the liquid state, however, was sudden, similar to what happens in ordinary three-dimensional materials.
Read more:
