Matter's temperature limit for a physical state

[Xyo II]

Ms Dawn's Pitch Drop Experiment thread brought up a question that I haven't found an answer to. Can one prove that a substance is at the limit of a phase? I guess I'm really asking, is it possible to calculate at what temperature one will find a phase boundary for a given element? Or is the definition of a phase of an element entirely dependent on measurements by experiment? I know that it's dependent on so many factors, and I'm not sure why I'm curious about this, but chemistry and quantum physics have always been a little boring to me, with all the little details and calculations. Thanks for any info!

 

[f95toli]

Originally posted by: Xyo II
I guess I'm really asking, is it possible to calculate at what temperature one will find a phase boundary for a given element?

Yes, you can. How difficult it is depends on which kind of phase transition you are talking about. A very good example is the phase transition from normal conduction to the superconducing state of a simple metals like aluminium; the critical temperature can be calculated to a very high precision using relatively simple formulas (for more complicated materials you need to use numerical methods).
If you mean "structural" phase transitions like e.g. melting etc that is also possible but in most cases you need to use numerical methods.

 

[jagec]

In my experience, any phase boundary simple enough to predict with equations has already been measured experimentally a million times already.