Tuning the Eu valence in EuPd_3B_x: pressure versus valence electron count - a combined computational and experimental study

TL;DR

This study combines computational and experimental methods to explore how pressure and electron count influence the Eu valence state in EuPd_3B_x, revealing that electron count primarily drives valence changes.

Contribution

It demonstrates that Eu valence in EuPd_3B_x is mainly affected by valence electron count rather than volume change, supported by combined theoretical calculations and experimental measurements.

Findings

Pressure partially suppresses Eu mixed-valence state.

Valence change driven mainly by added valence electrons from boron.

Predicted similar valence behavior in Eu_{1-x}La_xPd_3 for x >= 0.4.

Abstract

In a joint theoretical and experimental study we investigate the pressure dependence of the Eu valence in EuPd_3B_x (0 <= x <= 1). Density functional band structure calculations are combined with x-ray absorption and x-ray diffraction measurements under hydrostatic pressures up to 30 GPa. It is observed that the heterogenous mixed-valence state of Eu in EuPd_3B_x (x >= 0.2) can be suppressed partially in this pressure range. From the complementary measurements we conclude that the valence change in EuPd_3B_x is mainly driven by the number of additional valence electrons due to the insertion of boron, whereas the volume change is a secondary effect. A similar valence change of Eu in Eu_{1-x}La_xPd_3 is predicted for x >= 0.4, in line with the suggested electron count scenario.