I have a difficulty with thermodinamics theory

1. Oct 22, 2011

izik

Hi everybody. Can someone help me?

i have a difficulty with the definition of entropy for a gas in low temp. The difficulty risses in the different casses for the entropy of bose particles as well as the entropy of vibrating and rotating molecules. The mathematics is simplest in the case of vibrating diatomic molecules so ill keep with this example.
Assume a gas with N diatomic molecules with a given frequency w which defines a single energy quantum hw such that the vibrational energy of each molecule is a whole number of quantaq hw. assume that the total energy is Khw where K is a whole number signifficuntly smaller then N.
the number of quantum states is as far as I can see equivalent to the case of placing K identical balls in N boxes which gives N in power K divided by K!. The entropy is by definition KlnN-KlnK which is not aditive and does not coply from the results of applying Gibbes equation.
Every help is welcome