Water is an unusual shape may be the most common in the Universe

Recently in the Laboratory of laser energetics in Brighton, new York, one of the most powerful lasers in the world struck in a drop of water, creating a shock wave that raised the pressure in the water to millions of atmospheres, and temperature of thousands of degrees. X-rays that have passed through the drop to the same fraction of a second, showed mankind the first glimpse of water in such extreme conditions. They showed that the water within the shock wave did not become a superheated liquid or gas. No, the water was cold.

Paradoxically, the atoms of the water froze, forming crystalline ice. However, as predicted by physics, suradasa on the screens in the next room.

“You hear a shot and at the same time see that something interesting happened,” says Marius Millo from the Lawrence Livermore national laboratory. Lawrence, who conducted the experiment along with Federica Coppari.

What happens with water at high pressure and temperature?

The results of this work, published this week in Nature, confirms the existence of “superionic ice”, a new phase of water with bizarre properties. In contrast to the familiar ice that you can find in the freezer or the North pole, superionic ice is black and hot. Cube this ice weighed four times more than usual. For the first time its existence had been predicted more than 30 years ago, and although it has never been seen, scientists believe it may be one of the most common types of water in the Universe.

Even in the Solar system most of the water probably is in the form of superionic ice in the depths of Uranus and Neptune. Her more than of liquid water in Earth’s oceans, Europa and Enceladus. The discovery of superionic ice could solve old mysteries about the composition of these “ice giants”.

Scientists have found eighteen amazing ice crystal architectures, including hexagonal arrangement of water molecules in ordinary ice (Ih). After the ice-I, which is of two forms, Ih and Ic, the rest of the forms are numbered from II to XVII in the order of discovery. Yes, the “ice-9” really exists, but its properties are not the same as in the Kurt Vonnegut novel “cat’s Cradle”.

Superionic ice can lay claim to the mantle of ice-XVIII. It is a new crystal, but there’s just one thing. All previously known water ice consists of intact water molecules in which one atom of oxygen bound with two atoms of hydrogen. But superionic ice, as shown by a new measurement, not the same. It exists in a kind of surreal limbo, half solid, half liquid. Separate the water molecules apart. The oxygen atoms form a cubic lattice, but the hydrogen atoms are poured freely, flowing like liquid through a rigid cage of oxygen.

Experts say that the discovery of superionic ice justifies computer projections that can help physicists material scientists to create the future of substances with individual properties. But the discovery of this ice required ultra-fast measurement and precise control of temperature and pressure that became possible only in the conditions of improvement of experimental methods.

“All this was impossible to do, say, five years ago,” says Christoph Salzmann of University College London, who opened the ice-XIII, -XIV and XV. “It certainly will have a huge impact”.

Physicist Libya Bove from the National center for scientific research of France believed that since water molecules apart, it’s not quite a new phase of water. “This new state of matter, which is pretty impressive”.

Jigsaw puzzles on the ice

Physicists hunted for superionic ice for many years — ever since, as a primitive computer simulation of Pierfranco Demontis in 1988 predicted that the water will take this strange, almost metallic form if to push it beyond the map of the known ice phases.

Modeling has shown that under intense pressure and heat the molecules of water are destroyed. The oxygen atoms are in a cubic lattice, and “the hydrogen starts to jump from one position in a crystal to another, again and again,” says Millo. These jumps between lattice sites is so fast that the hydrogen atoms which are ionized, becoming, in effect, positively charged protons — acting as a liquid.

There was an assumption that the superionic ice will conduct electricity, such as metal, and hydrogen will play the role of electrons. The presence of these free hydrogen atoms will also increase the randomness of ice, its entropy. In turn, the increase of entropy make the ice more stable than other types of ice crystals, resulting in its melting point will rise.

Present it all easy believe it is difficult. The first models used simplified physics, trudging through the quantum nature of real molecules. Later the simulation added more quantum effects, but still spared the actual equations needed to describe the interaction of several quantum bodies that is too hard to calculate. Instead, they relied on approximation, increasing the likelihood that this scenario will prove to be a Mirage in the simulation. Experiments, meanwhile, could not create the necessary pressure and produce enough heat to melt is a solid substance.

And when all have abandoned this idea, planetary scientists have expressed their own suspicions that the water may be a superionic phase of ice. Around the same time when this phase was first predicted, the probe “Voyager-2” went in the outer solar system and found something strange in the magnetic fields of the ice giants Uranus and Neptune.

The fields around the other planets of the Solar system, appears to consist of strictly defined North and South poles, without much of the other structures. It seems like they are bar magnets, aligned with the axis of rotation. Planetary scientists attribute this to Dynamo: internal areas where conductive liquids rise and rotate as the rotation of the planet, creating a huge magnetic field.

On the contrary, the magnetic field emanating from Uranus and Neptune, seemed more cumbersome and complicated, with more than two poles. They also are not aligned closely to the rotation of their planets. One way to achieve this is to somehow restrict the conductive liquid, responsible for the Dynamo, only a thin outer shell of the planet, instead of letting her get inside the nucleus.

But the idea that these planets may have a solid core, unable to generate the Dynamo did not seem realistic. If you have drilled these ice giants, you would expect to first encounter a layer of ionic water, which will flow to conduct current and to participate in the Dynamo. It seems that even more in-depth material, even at higher temperatures will also be fluid, but it is naive. The planetary community has a joke about the fact that the depths of Uranus and Neptune can’t be solid. But it turned out that can.

Explosive ice

Coppari, Millo and their team assembled the pieces of the puzzle together.

In an earlier experiment, published in February 2018, physicists have obtained indirect evidence for the existence of superionic ice. They were squeezing a drop of room temperature water between the pointed ends of two cut diamonds. When the pressure has risen to about gigapascal that is about 10 times more than the bottom of the Mariana trench, the water turned into a tetragonal crystal, ice-VI. At 2 GPA, he moved into the ice-VII, denser, a cubic shape, transparent to the naked eye, which, as recently discovered by scientists, also exists in tiny pockets within the natural diamond.

Then, using the OMEGA laser at the Laboratory for laser energetics, Millo and his colleagues have zeroed in on the ice-VII, still squeezed between diamond anvils. When the laser struck the surface of the diamond, he vaporized material upward, essentially throwing the diamond in the opposite direction and sending a shock wave through the ice. Team Millo found that sverhodarennym ice melted at a temperature of 4700 degrees Celsius, as expected for superionic ice, and that it was electricity due to the movement of the charged protons.

After the predictions of the bulk properties of superionic ice has been confirmed, a new study Coppari and Millo had to confirm its structure. If you want to confirm the crystalline nature, you need the x-ray diffraction.

Their new experiment missed the ice-VI and ice-VII at all. Instead, the team just broke the water between the diamond anvils laser shots. After a billionth of a second, while the shock wave penetrated through and the water began to crystallize in the nanometer ice cubes, scientists have added another 16 laser beam to evaporate a thin piece of iron next to the sample. The resulting plasma poured crystallized water x-rays, which then diregiovani from ice crystals and allowed the team to discern their structure.

The atoms in water was converted to long-predicted but never-before-seen architecture, ice-XVIII: a cubic lattice with oxygen atoms at each corner and in the center of each face.

“This is a real breakthrough,” says Coppari.

“The fact that the existence of this phase is not an artifact of quantum molecular dynamic simulation, and it is really is very good,” says Bove.

And this kind of successful cross-validation as simulation and present superionic ice suggests that the ultimate “dream” of researchers in physics materials can be achieved. “You tell me what material properties you need, we go to the computer and theoretically find out which material and which crystal structure you need,” says Raymond Jeanloz, a scientist at the University of California at Berkeley.

The new analysis also suggests that although superionic ice actually conducts some electricity, it is rather loose, but solid. It will slowly spread, but the flow — no. Thus, fluid layers inside Uranus and Neptune can stay for about 8000 kilometers deep into the planet where it will start a huge mantle shaky superionic ice. This limits most of the action Dynamo at shallower depths, given the unusual fields of the planets.

Other planets and moons of the Solar system probably do not have the internal temperatures and pressures that would exist superionic ice. But many exoplanets of the size of the ice giants suggests that this substance — superionic ice will be distributed on icy worlds throughout the galaxy.

Of course, not one of the planets would contain only water. Ice giants in our Solar system are also involved from methane and ammonia. The degree to which the superionic behavior actually finds a place in nature, “will depend on whether there are these phases when we are mixing water with other materials,” say the researchers. However, superionic ammonia must also exist.

The experiments continue. Do you think we know one that is in the center of the largest bodies in our Solar system? Please share your opinion in our chat in Telegram.

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