A form of ice can be found in the Earth's mantle, as well as on large moons and planets covered in water.
The properties of ice and the process of its formation are notunique and reminiscent of other materials. This means that it changes with changes in temperature and pressure. Carbon functions according to the same logic, from which either diamond or graphite can be obtained. But there are exceptions, as scientists know that ice has more than twenty solid forms.
In their work, physicists used laser heating and a diamond anvil to discover a new form of ice.
Ice has over twenty solid shapes
How did the researchers find out about the new form of ice?
To begin with, water was placed in containers between two diamonds. This mechanism is called a diamond anvil cell.
It consists of two cone-shaped diamonds,located opposite each other over an area of 1 mm in diameter. With this, you can create a pressure of several million atmospheres. Diamond is also transparent, so the sample under study can be studied in different ways. Scientists have reproduced the pressure that exists in the center of our planet.
After that, the ice located between the diamonds was heated with a laser. It partially melted, and then turned into a large number of small crystals.
The scientists increased the pressure and found that the icewas in the well-known cubic form of Ice VII, and then turned into a new, unexplored, intermediate stage of Ice VIIT. They called it tetragonal. After that, the ice ended up in another already studied phase, Ice X.
Ice VII is a cubic phase of ice with a disordered arrangement of hydrogen atoms.
Ice X is a symmetrical phase in which the protons are ordered. It can be obtained at a pressure of 70 GPa.
According to the researchers, they drew attention to the fact that the Ice X shape was obtained at unexpectedly low pressure. It amounted to 300 thousand atmospheres, not 1 million.
“In our work, we have shown that it is possible to obtainIce X phase and do not use as high a pressure as intended. This is important information that we have received thanks to ultra-precise measurements,” said Ashkan Salamat, a physicist from the UNLV laboratory.
During the work, the researchers also used a supercomputer to simulate bond rewiring and to predict where a phase transition would occur.
Scientists increased the pressure and found that the ice was in the well-known cubic form Ice VII, and then turned into a new, unexplored and intermediate stage Ice VIIT
Does ice have many forms?
Yes, there are more than 20 forms of ice. We will list not all, but the first seven. Information about other species is publicly available.
- Amorphous ice is ice without a crystalline structure where the water molecules are arranged randomly. It's like atoms in regular glass.
- Ice Ih is regular hexagonal crystalline ice. It includes almost all existing ice in the biosphere.
- Ice Ic is a metastable cubic crystalline ice. It forms at -53°C: it can exist at temperatures as low as -33°C. This type of ice can form in the upper atmosphere.
- Ice II is a rhombohedral crystalline form with a highly ordered structure. This type of ice can be obtained from the previously mentioned Ice Ih by compressing it at -63°C to -83°C.
- Ice III is tetragonal crystalline ice and can be created at temperatures as low as -23 °C and pressure as low as 300 MPa.
- Ice IV is a metastable rhombohedral phase. This phase can be obtained by gradually heating amorphous ice at 810 MPa.
- Ice V is a monoclinic crystalline phase. It is formed when water is cooled to -20.15 °C and a pressure of 500 MPa.
Why can't a new phase of ice be found on Earth?
According to the authors, it is hardly possible to find a new phaseice on Earth, since there are no suitable conditions for its creation. But the conditions under which it is formed are in the mantle of our planet, as well as on large moons or on planets with a lot of water.
According to the authors, it is hardly possible to find a new phase of ice on Earth, since there are no suitable conditions for its creation.
Why do we need to know about the different forms of ice?
Large, water-rich planets are far from Earth and are not part of our solar system. Thanks to the new information, astronomers will be able to learn more about these objects.
This work will change scientists' understanding of the compositionexoplanets, said Ashkan Salamat, a physicist at the UNLV lab. The authors suggested that studying a new form of ice would help researchers learn more about possible extraterrestrial life outside our solar system.
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