The equipartition theorem states that the average energy of any quadratic degree of freedom is [tex]1/2 k T[/tex], such that the total thermal energy is [tex]U_{thermal} = Nf\frac{1}{2}kT [/tex] where f is the number of degrees of freedom.(adsbygoogle = window.adsbygoogle || []).push({});

When the temperature is high enough the vibration mode is excited and then we are to include a potential energy term for the energy coming from the bond between molecules, [tex]\frac{1}{2}kx^2[/tex] (At least according to my book).

I thought that the _thermal_ energy of a system was only associated with the kinetic enery of the molecules, but if this is right, what then is that potential energy term doing in my calculations?

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# Potential energy in the equipartition theorem.

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