A Denser Hydrogen Inferred from First-Principles Simulations Challenges Jupiter's Interior Models

TL;DR

This study uses advanced first-principles simulations to show that hydrogen is denser under planetary conditions than previously thought, impacting models of Jupiter's interior.

Contribution

It validates density functional theory functionals against higher-level quantum Monte Carlo methods to improve the accuracy of hydrogen's equation of state.

Findings

Hydrogen is denser at planetary conditions than current models suggest.

Different DFT functionals can qualitatively change pressure predictions.

Results imply Jupiter's interior models need revision with lower metallicity estimates.

Abstract

First-principle modeling of dense hydrogen is crucial in materials and planetary sciences. Despite its apparent simplicity, predicting the ionic and electronic structure of hydrogen is a formidable challenge, and it is connected with the insulator-to-metal transition, a century-old problem in condensed matter. Accurate simulations of liquid hydrogen are also essential for modeling gas giant planets. Here we perform an exhaustive study of the equation of state of hydrogen using Density Functional Theory and quantum Monte Carlo simulations. We find that the pressure predicted by Density Functional Theory may vary qualitatively when using different functionals. The predictive power of first-principle simulations is restored by validating each functional against higher-level wavefunction theories, represented by computationally intensive variational and diffusion Monte Carlo calculations. Our simulations provide evidence that hydrogen is denser at planetary conditions, compared to currently used equations of state. For Jupiter, this implies a lower bulk metallicity (i.e., a smaller mass of heavy elements). Our results further amplify the inconsistency between Jupiter's atmospheric metallicity measured by the Galileo probe and the envelope metallicity inferred from interior models.