Diamonds can withstand little pressure. In fact, he reviews that – diamonds can withstand high pressure. In a series of new experiments, scientists have discovered that diamonds retain their crystal structure at pressures five times higher than that of the Earth’s core.
This contradicts the predictions that the diamond should turn into an even more stable structure at extremely high pressure, suggesting that the diamond sticks to a shape under conditions where another structure would be more stable, which is called ” metastable ”.
The discovery has implications for modeling high-pressure environments, such as the nuclei of carbon-rich planets.
Carbon is just as common as it gets. It is the fourth most abundant element in the Universe and can be found in exoplanets and stars and in the space between them. It is also a major ingredient of all known life on Earth. Without it, we would not exist; that is why we refer to ourselves as a carbon-based life.
Thus, carbon is of great interest to scientists of all kinds. However, a place where carbon can be found – the nuclei of carbon-rich exoplanets – is very difficult to study. The high pressures present there are difficult to reproduce and, once the high pressures are reached, the material that is squeezed is difficult to probe.
We know that carbon has several allotropes, or variant structures, at ambient pressures that have significantly different physical properties. Coal, graphite and diamond are formed at different pressures, the diamond appears at higher pressures deep underground, starting with about 5 or 6 gigapascals.
The pressure in the Earth’s core is up to 360 gigapascals. At even higher pressures – about 1,000 gigapascals, just over 2.5 times the Earth’s core pressure, scientists have predicted that carbon will turn back into more new structures, which it does not. -I’ve seen or realized before.
One method of achieving extremely high pressures involves the use of a diamond anvil and shock compression. With this method, the hydrocarbons were subjected to 45,000 gigapascals. This method tends to destroy the sample before its structure can be probed.
A team led by physicist Amy Lazicki Jenei of the Lawrence Livermore National Laboratory has found another way to make it work. They used ramp-shaped laser pulses to squeeze a solid carbon sample at a pressure of 2,000 gigapascals. At the same time, the nanosecond time-resolved X-ray diffraction was used to test the crystal structure of the sample.
This doubled the previous pressure at which a material was probed using X-ray diffraction. And the results surprised the team.
“We found that, surprisingly, under these conditions, the carbon does not turn into any of the predicted phases, but keeps the structure of the diamond to the highest pressure,” Jena said.
“The same ultra-strong interatomic bonds (which require high energies to break), which are responsible for the metastable diamond structure of carbon that persists indefinitely at ambient pressure, also prevent its transformation into over 1000 gigapascals in our experiments.
In other words, the diamond does not relax back into graphite when it is taken out of the underground depths: from higher to lower pressures. The force preventing this reversal could be the reason why the diamond does not rearrange itself in another allotrope at pressures even higher than those in which it was formed.
This discovery could change the way scientists model and analyze carbon-rich exoplanets, including the mythical diamond planets.
In the meantime, I am still working to understand the result. The team is not entirely sure why the diamond is so strong – more research will be needed to find out why the diamond is metastable in a wide range of pressures.
“Whether nature has found a way to overcome the high energy barrier to the formation of predicted phases inside exoplanets is another open question,” Jena said.
“Subsequent measurements using an alternative compression pathway or starting from an allotropic carbon with an atomic structure that requires less energy to rearrange will provide additional information.”
The research was published in The nature.