Dielectric relaxation of hot water

Dielectric relaxation of water for a wide range of temperature (373 K less than or equal to T less than or equal to 973 K) and density (0.07 g cm(-3)l ess than or equal to d less than or equal to 0.66 g cm(-3)) is studied with the molecular dynamics simulation technique. The evolving water electronic structure is explicitly incorporated via the truncated adiabatic basis-set representation. For a given density, polarization dynamics of water tends to become faster with increasing temperature. At reduced densities, it show s a marked deviation from a single exponential decay. Another interesting f eature is that at fixed T, water dielectric relaxation becomes, in general, accelerated as the density decreases. This trend is at variance with recen t microwave spectroscopy measurements at elevated temperatures and reduced densities. Possible sources for the discrepancy between the simulation and experimental results are discussed. (C) 2000 American Institute of Physics. [S0021-9606(00)51939-4].