Statistical Thermodynamic Theory of Liquid Water

A new statistical thermodynamic theory is presented for a model of liquid water, which consists of two components, i.e., tetrahedrally-coordinated pentamers and non-hydrogen-bonded monomers. In the model the two components are assumed to be immersed in a uniform background potential which results from electrostatic, induction, and dispersion forces between water molecules. A partition function is given without assuming any specified lattice. A translational partition function is written into a simple and explicit expression which is derived from the Lebowitz solution of the Percus-Yevick equation for hard sphere mixtures. The mole fraction of each component and the density are determined by solving two equations, i.e., the condition of free energy minimization and the equation of state derived from the partition function, simultaneously. Various thermodynamic quantities are calculated and the values determined are compared with those observed. Some discussions are carried out, together with the criticism of the earlier theories.