Structure, equation of state, diffusion and viscosity of warm dense Fe under the conditions of giant planet core

TL;DR

This study uses first-principles quantum Langevin molecular dynamics to analyze the structural, thermodynamic, and transport properties of warm dense iron at conditions relevant to giant planet cores, highlighting the importance of the Stokes-Einstein relation.

Contribution

First-principles calculations of warm dense Fe properties at giant planet core conditions, including validation of the Stokes-Einstein relation in extreme regimes.

Findings

Fe exhibits specific ionic structures at high densities and temperatures.

The equation of state data for Fe under these conditions are provided.

The validity of the Stokes-Einstein relation depends on the choice of effective atomic diameter.

Abstract

Fe exists abundantly in the universe. In particular, the dynamical structures and transport properties of warm dense Fe are crucial for understanding the evolution and structures of giant planets. In this article, we present the ionic structures, equation of states, diffusion and viscosity of Fe at two typical densities of 33.385 g/cm$^3$ and 45 g/cm$^3$ in the temperature range of 1 eV and 10 eV, giving the data by the first principles calculations using quantum Langevin molecular dynamics (QLMD). Furthermore, the validation of Stokes-Einstein (SE) relation in this regime is discussed, showing the importance of choosing the effective atomic diameter. The results remind us of the careful usage of the SE relation under extreme conditions.