Topological Electride Phase of Sodium at High Pressures and Temperatures

TL;DR

This study predicts a high-pressure phase transition in sodium to a topological electride with unique electronic properties, revealing complex behaviors in warm dense sodium under extreme conditions.

Contribution

First prediction of a topological electride phase in sodium at high pressures and temperatures using ab initio methods.

Findings

Na transitions to P63/m phase between 200 GPa and 350 GPa.

P63/m Na is a topological semimetal with a Dirac nodal surface.

The phase features localized non-nuclear charge in honeycomb channels and cages.

Abstract

Ab initio evolutionary structure searches coupled with quasiharmonic calculations predict that the insulating Na hP4 phase transitions to a novel P63/m phase between 200 GPa at 150 K, and 350 GPa at 1900 K. P63/m Na is a topological semimetal with a Dirac nodal surface that is protected by a non-symmorphic symmetry, S2z . It is characterized by localized non-nuclear charge within 1D honeycomb channels and 0D cages rendering it an electride. These results highlight the complexity of warm dense sodiums electronic structure and free energy landscape that emerges at conditions where ionic cores overlap.