Une nouvelle forme de glace découverte à très haute pression

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Top Highlights

• This new "form" of ice does not exist on the surface of the Earth

• It is added to the twenty crystalline forms already known.

• hexagonal symmetry or Ice-I which consists of an oxygen atom placed in the center of a regular tetrahedron formed by four other oxygen atoms

• hydrogen bonds

• This structure is found in snowflakes and in frost or at the bottom of your freezer, but also in the nevées, i.e. the accumulations of snow which last all year beyond the limit eternal snow in the mountains

• At normal atmospheric pressure, i.e. 101,325 Pa, water turns into ice by taking a hexagonal crystal structure when its temperature drops below the melting temperature which is 0 ° C

• pressure becomes greater, the ice adopts sometimes amazing crystal structures

• To create this new form of ice, scientists have indeed had to reach colossal pressures. They used an anvil cell to do this, which is a laboratory device used to subject material samples to high pressures and temperatures

• geologists to reproduce the pressure and temperature conditions that prevail inside the earth's mantle

• anvil cell

• tangle of crystals

• melted the sample to refrost it by applying some pressure to it

• laser

• By gradually increasing the pressure with laser heating each time, they arrived at different varieties of arrangement for the oxygen and hydrogen atoms

• hydrogen and oxygen atoms take turns

• In two of these phases, the ice formed had a cubic structure

• Ice-VII, the hydrogen atoms are messy

• Ice-X is more symmetrical

• a few tens to several hundred thousand times the atmospheric pressure at sea level

• intermediate phase called Ice -VIIt