The Structure of Eu-III

TL;DR

This study re-examines the high-pressure phases of europium, revealing that Eu remains hcp up to 33 GPa and identifying impurity phases and complex structural transitions at higher pressures.

Contribution

It provides new x-ray diffraction data showing Eu's phase stability up to 33 GPa and clarifies the nature of impurity and high-pressure phases.

Findings

Eu remains hcp up to 33 GPa

Impurity phase with space group R-3c appears at 18 GPa

Complex distorted hcp phase emerges above 33 GPa

Abstract

Previous x-ray diffraction studies have reported Eu to transform from the hcp structure to a new phase, Eu-III, at 18 GPa. Using x-ray powder diffraction we have determined that Eu remains hcp up to 33 GPa, and that the extra peaks that appear at 18 GPa are from an impurity phase with space group R-3c . Above 33 GPa the diffraction pattern becomes very much more complex, signalling a transition to a phase with a distorted hcp structure.