Electronic structure and superconductivity of Europium

TL;DR

This study investigates the electronic structure and superconductivity of europium under pressure, using advanced computational methods to match experimental phase and superconducting transition data.

Contribution

It introduces a semi-empirical shift of f-states in calculations, accurately predicting europium's phase ordering, lattice parameters, and superconducting behavior under pressure.

Findings

Correct phase ordering and lattice parameters for Eu.

Superconducting transition temperature trends match experimental data.

Pressure-dependent electronic structure aligns with observations.

Abstract

We have calculated the electronic structure of Eu for the bcc, hcp, and fcc crystal structures for volumes near equilibrium up to a calculated 90 GPa pressure using the augmented-plane wave method in the local-density approximation. The frozen-core approximation was used with a semi-empirical shift of the f-states energies in the radial Schr$\ddot{o}$dinger equation to move the occupied 4f valence states below the $\Gamma_1$ energy and into the core. This shift of the highly localized f-states yields the correct europium phase ordering with lattice parameters and bulk moduli in good agreement with experimental data. The calculated superconductivity properties under pressure for the $\it bcc$ and $\it hcp$ structures are also found to agree with and follow a $T_c$ trend similar to recent measurement by Debessai et al.$^1$