New Phase Transition of Lanthanum at High Pressure

TL;DR

This paper reports the discovery of a new body-centered tetragonal phase of metallic lanthanum at 190 GPa, revealing an expanded phase transition sequence and unusual packing behavior under high pressure.

Contribution

It introduces a previously unreported $bct$ phase of lanthanum at high pressure, expanding understanding of its phase transition sequence and structural properties.

Findings

New $bct$ phase identified at 190 GPa

Phase transition sequence extended to include $bct$ phase

Unusual non-closed packing behavior at high pressure

Abstract

Lanthanum (La), the first member of the rare-earth elements, recently aroused strong interest due to its unique superhydride with superconducting properties. Although there is much theoretical and experimental work about phase transitions and superconductivity in metallic La, we got a new body-centred tetragonal ($bct$) phase in metallic La with space group $I4/mmm$ at $190$ GPa exchanging from face-centered cubic ($fcc$) phase in previous work, which expanded the phase transition sequence. The $bct$ phase shows an abnormal packing way that turned to non-closed packing at high pressure. And more detailed properties of the new phase are discussed.