  We study water-hydrogen mixtures under planetary interior conditions using ab
initio molecular dynamics simulations. We determine the thermodynamic
properties of various water-hydrogen mixing ratios at temperatures of 2000 and
6000 K for pressures of a few tens of GPa. These conditions are relevant for
ice giant planets and for the outer envelope of the gas giants. We find that at
2000 K the mixture is in a molecular regime, while at 6000 K the dissociation
of hydrogen and water is important and affects the thermodynamic properties. We
study the structure of the liquid and analyze the radial distribution function.
We provide estimates for the transport properties, diffusion and viscosity,
based on autocorrelation functions. We obtained viscosity estimates of the
order of a few tenths of mPa.s for the conditions under consideration. These
results are relevant for dynamo simulations of ice giant planets.
