Liquid Diamonds: A Mystery of Gas Giants

[lavinia]

TL;DR Summary

Liquid diamonds may occur in the interior of gas giants such as Neptune and Uranus. What is a liquid diamond?

Liquid diamonds apparently may form in gas giants where huge atmospheric pressure compresses carbon into diamonds that are then liquified as they fall downward into zones of increasing pressure. I thought a diamond was a crystal structure of carbon. How can this also be a liquid?

https://phys.org/news/2010-01-ocean...S2kAKuWU8G_WVLGGF7PgFZ7nakZP3htOKtsmOse1IY_ek

 

[Ygggdrasil]

The Phys Org article appears to be referencing this paper published in the journal Nature Physics:

Eggert et al. Melting temperature of diamond at ultrahigh pressure. Nature Physics 6:40 2010
https://www.nature.com/articles/nphys1438

Abstract:

Since Ross proposed that there might be ‘diamonds in the sky’ in 1981 (ref. 1), the idea of significant quantities of pure carbon existing in giant planets such as Uranus and Neptune has gained both experimental2 and theoretical3 support. It is now accepted that the high-pressure, high-temperature behaviour of carbon is essential to predicting the evolution and structure of such planets4. Still, one of the most defining of thermal properties for diamond, the melting temperature, has never been directly measured. This is perhaps understandable, given that diamond is thermodynamically unstable, converting to graphite before melting at ambient pressure, and tightly bonded, being the strongest bulk material known5,6. Shock-compression experiments on diamond reported here reveal the melting temperature of carbon at pressures of 0.6–1.1 TPa (6–11 Mbar), and show that crystalline diamond can be stable deep inside giant planets such as Uranus and Neptune1,2,3,4,7. The data indicate that diamond melts to a denser, metallic fluid—with the melting curve showing a negative Clapeyron slope—between 0.60 and 1.05 TPa, in good agreement with predictions of first-principles calculations8. Temperature data at still higher pressures suggest diamond melts to a complex fluid state, which dissociates at shock pressures between 1.1 and 2.5 TPa (11–25 Mbar) as the temperatures increase above 50,000 K.

The article explores the behavior of carbon at high temperatures and pressures by exerting high pressures and temperatures on diamond in order to find its melting point. Nowhere in the paper does the term "liquid diamond" appear. Therefore the concept of a "liquid diamond" seems to be made up by a confused science journalist at Phys Org (probably a good reason not to trust materials they put out).

 

[lavinia]

The Phys Org article appears to be referencing this paper published in the journal Nature Physics:

Eggert et al. Melting temperature of diamond at ultrahigh pressure. Nature Physics 6:40 2010
https://www.nature.com/articles/nphys1438

Abstract:

The article explores the behavior of carbon at high temperatures and pressures by exerting high pressures and temperatures on diamond in order to find its melting point. Nowhere in the paper does the term "liquid diamond" appear. Therefore the concept of a "liquid diamond" seems to be made up by a confused science journalist at Phys Org (probably a good reason not to trust materials they put out).

This is not the only reference.In any case, it is not a linguistic question but a question about crystals at high temperatures.

 

[Vanadium 50]

Diamond is a crystal, and so has short-range order. Liquids don't - they have only long-range order. So you are right, "liquid diamond" makes no sense. (But "liquified diamond" does)

 

[lavinia]

Diamond is a crystal, and so has short-range order. Liquids don't - they have only long-range order. So you are right, "liquid diamond" makes no sense. (But "liquified diamond" does)

I really didn't ask this to be corrected on vocabulary. I was trying to start a potentially interesting conversation.

https://www.nature.com/articles/nphys1438

But that's ok. I can just read some papers.

 

[Vanadium 50]

I apologize for agreeing with you.