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Confused by some aspects of thermodynamics

  1. May 8, 2005 #1
    I am quite confused by some aspects of thermodynamics. First of all, I just wonder, when the textbook says that "when the constraints are temperature, volume and particle number, minimise F for equilibrium" (and similar statements for G and H), does it mean that the temperature, volume and particle number of the sub-system (i.e. excluding the reservoir) is fixed?

    And also, if Z, the partition function, is given, how should I proceed to find the equation of state?

    Thank you. :tongue2:
     
  2. jcsd
  3. May 8, 2005 #2
    Because
    [tex]dF \leq -SdT -PdV + \mu dN[/tex]
    then at fixed volume , temperature, and particle number, the free energy can only decrease, if we are at non-equilibrium. Thus temperature, volume, and particle number called "natural" arguments for the free energy.

    If you know a partition function, you can calculate free energy. After that you can find pressure, enthropy, and thermodynamic potential using the thermodynamic identities
     
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