Effect of the spin-orbit interaction on thermodynamic properties of liquid uranium

TL;DR

This study uses quantum molecular dynamics to show that including spin-orbit interaction significantly affects the thermodynamic properties of liquid uranium, especially its thermal expansion and density at melting point.

Contribution

First quantum molecular dynamics calculation of uranium considering spin-orbit coupling, revealing its impact on thermodynamic properties and density.

Findings

Spin-orbit interaction increases thermal expansion of uranium.

Relativistic effects are crucial for matching experimental density.

Spin-orbit effects influence thermodynamic properties at high T and P.

Abstract

We present the first quantum molecular dynamics calculation of zero-pressure isobar of solid and liquid uranium that account for spin-orbit coupling. We demonstrate that inclusion of spin-orbit interaction leads to higher degree of the thermal expansion of uranium, especially in the liquid phase. Full accounting of relativistic effects for valence electrons, particularly spin-orbital splitting of the 5f band, is substantial for the reproduction of the experimental density of molten uranium at the melting temperature. Influence of the spin-orbit interaction on the thermodynamic properties at high temperatures and pressures is also analyzed.