Thermal Conductivity of Hydrogen at High Pressure and High Temperature: Implications to Giant Planets

Abstract

Hydrogen (H2) is the most abundant constituent in giant planets, but its thermal conductivity Λ under extreme pressure-temperature (P-T) conditions remains largely unknown. Here we report the Λ of H2 from ambient to 60.2 GPa at 300 K and from 300 to 773 K at 2.1 GPa. At 300 K, the Λ of liquid H2 fluctuates at ∼0.7–1.1 W m−1 K−1. Upon crystallization to H2-I phase, the Λ jumps to 5.5 W m−1 K−1 at 7.2 GPa, and monotonically increases with pressure to ∼27 W m−1 K−1 at 60.2 GPa. Upon heating, the Λ of liquid H2 at 2.1 GPa scales with T0.68. Moreover, the density (ρ)-dependent compressional sound velocity (Vp) of liquid and solid H2 derived from Brillouin frequency data both follow the Birch's law. Besides the novel insights into the physics of thermal transport in H2 under extreme conditions, our results significantly advance the modeling of Λ-Vp-ρ relationship in a planet with H2.