Water dimers in the atmosphere III: Equilibrium constant from a flexible potential

The new results for the water dimer equilibrium constant, K(sub p)(T) in the range 190-390 K, using a flexible potential energy surface fitted to spectroscopical data are presented. The newly calculated values for K(sub p)(T) are in very good agreement with available experimental data at room temperature, and at higher temperatures, with the analysis of the convergence of the partition function reveals that quasi-bound states are likely to contribute to the equilibrium constant.