Heat capacity of the generalized two-atom and many-atom gas in nonextensive statistics

We have used the generalized two-atom ideal gas model in Tsallis statistics for the statistical description of a real gas. By comparing the heat capacity with the experimental results for the two-atom molecule gases such as N2, O2 and CO, we find that these gases appear to be extensive at normal temperature, but they may be nonextensive at a lower temperature. Furthermore, we study the relation between the heat capacity and the degree of freedom. We find the limiting value of entropic index q as a function of the degree of freedom, q<2g+1, for the heat capacity to be finite. In addition, for the gas molecule with a high degree of freedom, a weak nonextensivity of 1−q<0 can lead to instability.