Using the rst law of thermodynamics (1.16), we see that something special happens
when we keep volume constant: the work done term drops out and we have
CV = T
S
T
(1.18)
V
This form emphasises that, as its name suggests, the heat capacity measures the ab
1. The Fundamentals of Statistical Mechanics
Ludwig Boltzmann, who spent much of his life studying statistical mechanics, died in 1906 by his own hand. Paul Ehrenfest, carrying on the work,
died similarly in 1933. Now it is our turn to study statistical m
If we now include the translational contribution (2.5), the partition function for a diatomic molecule that can spin and move, but cant vibrate, is given by Z1 = Ztrans Zrot
N
(kB T )5/2 , and the partition function for a gas of these object Z = Z1 /N!,