Prediction of the Ideal-Gas Thermodynamic Properties for Water

We report a suitable analytical representation of the ideal-gas Gibbs free energy for water, and also derive an efficient analytical representation of the ideal-gas entropy from the former expression. These two analytical representations only involve six molecular constants of water, whereas the conventional computation schemes require a great many experimental spectroscopy data or calorimetric data. The predicted results for the Gibbs free energies and entropy values of water are in excellent agreement with available experimental data. The present study provides a novel pathway of treating the anharmonic vibrations of the water molecule.