- #1
RJC
- 8
- 0
Liquid sodium can exist at room temperature at EXTREMELY high pressures. Why?
Liquid Sodium: Room Temp & High Pressure
- Context: Graduate
- Thread starter RJC
- Start date
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Discussion Overview
The discussion centers on the conditions under which liquid sodium can exist at room temperature, particularly focusing on the role of high pressure and the structural transitions of sodium at these conditions. The conversation explores theoretical aspects of phase transitions and melting points in relation to sodium's crystalline structure.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant asserts that liquid sodium can exist at room temperature under extremely high pressures, questioning the underlying reasons.
- Another participant suggests that any liquid can exist at any temperature if the pressure is sufficiently high, with exceptions for substances that do not have a liquid state at certain temperatures.
- A participant proposes that the existence of a liquid phase with higher density is key, noting that sodium typically crystallizes in a body-centered cubic (bcc) structure, which is not close packed.
- It is mentioned that at high pressures, sodium may transition to a cubic or hexagonally close packed structure, potentially having a melting point below room temperature.
- Another participant agrees with the previous point but adds that many metals lacking a close-packed structure exhibit negative melting behavior, which is particularly pronounced in sodium.
- A reference to a recent paper is provided, indicating ongoing research in this area, although the participant has not yet read it.
Areas of Agreement / Disagreement
Participants express differing views on the mechanisms behind liquid sodium's existence at room temperature under high pressure, with no clear consensus reached on the specifics of the phase transitions or the implications of negative melting behavior.
Contextual Notes
The discussion includes assumptions about the behavior of sodium under pressure and the definitions of liquid states, which may not be universally agreed upon. The references to external papers suggest that the topic is still under investigation and may have unresolved aspects.
- #2
Claude Bile
Science Advisor
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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.
Claude.
- #3
Pieter Kuiper
- 142
- 0
That must be because there is a liquid phase with higher density.RJC said:
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.
Last edited:
- #4
Gokul43201
Staff Emeritus
Science Advisor
Gold Member
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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.Pieter Kuiper said:
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
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