Why does liquid sodium exist at room temperature under extreme pressure?

[RJC]

Liquid sodium can exist at room temperature at EXTREMELY high pressures. Why?

 

[Claude Bile]

Any liquid can exist at any temperature provided the pressure is high enough (except of course at temperatures where the substance in question does not have a liquid state such a dry ice).

Claude.

 

[Pieter Kuiper]

Liquid sodium can exist at room temperature at EXTREMELY high pressures. Why?

That must be because there is a liquid phase with higher density.

Normally, sodium crystallizes in the body-centered cubic (bcc) structure, which is not close packed. At high pressures there is probably a transition to cubic or hexagonally close packed. This structure may have a melting point below room temperature.

 

[Gokul43201]

That must be because there is a liquid phase with higher density.

Normally, sodium crystallizes in the body-centered cubic (bcc) structure, which is not close packed. At high pressures there is probably a transition to cubic or hexagonally close packed. This structure may have a melting point below room temperature.

This is exactly right, but it appears that there's more to it than just that. Most metals that lack a close-packed structure exhibit some degree of negative melting. In sodium, however, this is unusually strong.

There's a very recent paper on this that I've yet to read : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000094000018185502000001&idtype=cvips&gifs=yes

http://physics.about.com/od/thermodynamics/a/roomtempNaLiqui.htm