The Structure Theory of Water. III. The Order-Disorder Theory

Taking into account the cooperative nature of cluster formation, we applied the order-disorder theory, using Bragg and Williams’s approximation, to liquid water based on a two state model. The two state model consists of hydrogen-bonded molecules arrayed on α-sites in a tetragonal lattice and non hydrogen-bonded molecules on β-sites in the lattice. A partition function was formulated and calculated. The calculated energy difference, ε, between the molecules on β-sites and those on α-sites decreased continuously with the rise of temperature. Thermodynamic variables of liquid water were calculated at each temperature, where no adjustable parameter was used. Agreement between calculated values and observed ones is fairly good.