Abstract:

Since 1990, the PVT data of supercritical water from experiments and molecular dynamics simulations are extended to
very high temperatures and pressures. These data are assessed in detail in this work. The equation of state for water developed by
the International Association for the Properties of Water and Steam (IAPWS95) is chosen as a reliable basis for the assessment,
which is also aided by appropriate extrapolation of the equation. The results suggest that the simulated data of Zhang and Duan
(2005) and those of Abramson and Brown (2004) derived from sound velocity measurements agree well with those of the most
accurate data of water at present, but the latter has small systematic deviations. The data in the other groups have obvious
systematic deviations or uncertainties. The simulated data of Belonoshko and Saxena (1991) have a large P -T range, but they also
have large uncertainties and obvious systematic deviations. The simulated data of Brodholt and Wood (1993) also have notable
systematic deviations. As pressure increases, the volume deviations of these two groups of simulated data vary from positive to
negative, where the deviations in the latter group are particularly obvious, and show very strong pressure dependence features at
high pressures, so they are easy to correct. The experimental data of Withers et al. (2000), Brodholt and Wood (1994) and Frost and Wood (1997) have obvious positive deviations, and can be corrected in principle, where the deviations of the first group are small,
but those of the latter two are much bigger. Overall, the experimental data of Larrieu and Ayers (1997) have large uncertainties,
where small deviations are only limited to the data at specific temperature and pressure, and the deviations of the other data have
no obvious regularity. These results should be helpful in the correct use of and further refinement of the above data.

Key words: supercritical water, PVT properties, equation of state, molecular dynamics simulation