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in this wikipedia article regarding diamond anvils, it mentions that the pressure peaks roughly at 300 GPa.

My question is why is this so? is the diamond crystal structure collapsing if higher pressures are applied (like 500-600 Gpa, where metallic hydrogen is expected to form? and if such collapse happens, what sort of phase does the diamond collapses into?

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1 Answer 1

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The compressive strength of a perfect diamond cristal is in the range of 220–470 GPa, depending on the direction you compress. (X. Luo et al, J. Phys. Chem. C 2010, 114, 17851–17853; DOI: 10.1021/jp102037j)

To cite this article’s introduction:

Usually, diamond is used under nonhydrostatic conditions, such as a diamond indenter in the nanoindentation test and as diamond tips of the diamond anvil cell (DAC) in ultrahigh-pressure research. Therefore, theoretical investigations into the mechanical properties of diamond under nonhydrostatic conditions should be important. […]

In experimental work, the compressive strength of diamond can be roughly obtained from the strength of DAC.

And the conclusion:

From the mechanism under compressive deformation of diamond, we can estimate that the limit strength of DAC should be about 470 GPa.

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