Thermodynamics of Linear Molecules at High Temperature: C3O2 and C5

In this paper we derive equations for the classical partition function of a linear molecule, taking account of anharmonicity and rotation–vibration interaction. We calculate the thermodynamic properties of C₃O₂ and C₅ using a potential suggested by Morino, Kuchitsu, and Tanimoto. This potential, as well as a number of others, gives good agreement with the measured value of ${\mathrm{S°}}_{230}$ for C₃O₂ of McDougall and Kilpatrick.