In part I, the various thermodynamic properties of water are explained by using a modified significant structure model of water and considering the differences between the liquid solid-like structure and the infinite hydrogen bonding network of ice-I. The thermodynamic properties of heavy water are also explained by using isotopic mass and its related molecular properties. The breaking of hydrogen bonds is cooperative and is related to the total intermolecular vibrational energy. A five memebered ring connection is plausible for water cluster. The anomalies of supercooled state of water are explained with the two-structure model.
In part II, the significant structure theory of liquids is tested by evaluating the radial distribution function. The calculations are base on face-centered cubic quasi-lattice structure, and the fluctuation in volume is used to describe the thermal displacements of molecules. It is shown that the local structure of liquids has inhomogeneous distributions. The correlation at long ranges becomes negligible because of the fluidized vacancies in our model. The calculations are performed for liquid argon, and the results are in good agreement with experiments.
In part III, a procedure is shown that a new integral equation for the correlation function can be derived by assuming a functional of 1-particle distribution function and external field. The equation gives better result in high density case than the Percus-Yevick equation does and the same results with Percus-Yevick equation for hard sphere fluid. And the condition of solid-fluid phase transition is derived in the hard sphere system using the diagramatic approaches. The condition turns out that the Percus-Yevick and the hyper-netted chain approximation never show the solid-fluid phase transition. The gas-liquid transition does not exist in hard sphere system.