In this study, modified hyperbolical-type oscillator was used to simulate the internal vibration of a diatomic molecule. By employing the expression of partition function of the system, new analytical equations for the prediction of molar entropy, enthalpy, Gibbs free energy, and isobaric specific heat capacity were derived. The thermodynamic equations were applied to ground-state phosphorus dimer. Average absolute deviations of 0.3795, 0.8939, 0.3895, and 0.6978% were obtained. The results are in good agreement with existing data on gaseous phosphorus molecules in the literature.