Na-Au intermetallic compounds formed under high pressure at room temperature

TL;DR

This study reveals the formation of four distinct Na-Au intermetallic phases under high pressure at room temperature, expanding understanding of their structural evolution up to 60 GPa.

Contribution

The paper reports the discovery and structural characterization of four new Na-Au intermetallic phases formed under high pressure at room temperature.

Findings

Four Na-Au intermetallic phases identified up to 60 GPa.

Structural transformations occur at specific pressures.

High-pressure conditions induce large structural disorder in phase IV.

Abstract

High-pressure powder x-ray diffraction experiments have revealed that sodium and gold react at room temperature and form new Na-Au intermetallic compounds under high pressure. We have identified four intermetallic phases up to 60 GPa. The first phase (phase I) is the known Na2Au with the tetragonal CuAl2-type structure. It changed to the second phase (phase II) at about 0.8 GPa, which has the composition Na3Au with the trigonal Cu3As-type or hexagonal Cu3P-type structure. Phase II further transformed to phase III at 3.6 GPa. Phase III has the same composition Na3Au with the cubic BiF3-type structure. Finally, phase III changed to phase IV at around 54 GPa. Phase IV gives broad diffraction peaks, indicating large structural disorder.