THEORETICAL CALCULATION OF THE STATIC DIELECTRIC-CONSTANT OF WATER ATHIGH-TEMPERATURES AND PRESSURES

We report a computationally efficient method for the quantitative pred iction of the static dielectric constant (epsilon) of water at high te mperatures and pressures. Values of epsilon in this regime are needed in geochemistry for the prediction of ionic solubilities in hydrotherm al fluids. The method involves the application of a recently derived p erturbation theory to the SPCE model of water. The experimental databa se for epsilon in this regime is sparse, and the alternative computati onal procedure-a direct simulation-is 1-4 orders of magnitude slower t han the method we present. We find that the calculation provides quant itatively accurate values of epsilon for water provided y less than or equal to 2.4, where y is the ''dipolar strength function'' (=(4 pi/9) mu(2) rho/kT).