Thermodynamic functions of the improved Scarf II oscillator

Abstract In this study, the improved Scarf II oscillator was used to model the internal vibration of a diatomic molecule. By employing the equation of energy levels of the oscillator, the canonical partition function was obtained and used to derive analytical expressions for the prediction of molar entropy, enthalpy and isobaric heat capacity of substances. The thermodynamic models were used to analyze the thermodynamic properties of some diatomic molecules including BBr, PN, PO, and PCl. The average absolute deviation from experimental data was used to affirm the suitability of the models. The expression for the reduced molar enthalpy yielded an average absolute deviation of 1.0945%, 1.6959%, 1.0013%, and 1.0945% for the molecules. Average deviations of 1.3053%, 1.5024%, 1.3838%, and 0.7490% were also obtained using the heat capacity model. These results are in good agreement with the existing literature data on selected diatomic molecules.