W:ideal gas heat capacity

"I have been using Chem3D to calculate vibrational frequencies using
 MOPAC (FORCE THERMO PRECISE) and a PM3 method.  The printout gives heat capacity
 which looks like Cp for propane and Cv for 1,1,1-trifluoropropane.  Is there an
 extra correction that needs to be made when calculating the ideal gas heat
 capacity of fluorine containing molecules from the vibrational
 One of our users asked this question, but I am having difficulty in finding him
 a solution.  I thought I would check with the experts on this list for any
 Rich Talbot
 rtalbot () cambridgesoft.com