**Thermal Conductivity of Water at Extreme Conditions**

CZ Zhang and M Puligheddu and LF Zhang and R Car and G Galli, JOURNAL OF PHYSICAL CHEMISTRY B, 127, 7011-7017 (2023).

DOI: 10.1021/acs.jpcb.3c02972

Measuring the thermal conductivity (& kappa;)of water at extremeconditions is a challenging task, and few experimental data are available.We predict & kappa; for temperatures and pressures relevant to theconditions of the Earth mantle, between 1,000 and 2,000 K and up to22 GPa. We employ close to equilibrium molecular dynamics simulationsand a deep neural network potential fitted to density functional theorydata. We then interpret our results by computing the equation of stateof water on a fine grid of points and using a simple model for & kappa;.We find that the thermal conductivity is weakly dependent on temperatureand monotonically increases with pressure with an approximate square- rootbehavior. In addition, we show how the increase of & kappa; at highpressure, relative to ambient conditions, is related to the correspondingincrease in the sound velocity. Although the relationships betweenthe thermal conductivity, pressure and sound velocity establishedhere are not rigorous, they are sufficiently accurate to allow fora robust estimate of the thermal conductivity of water in a broadrange of temperatures and pressures, where experiments are still difficultto perform.

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