Low temperature phase of AuSn$_{4}$ induced by the van der Waals interactions

TL;DR

This study reveals that the low-temperature phase of AuSn₄ is stabilized by van der Waals interactions, with a dynamically stable structure identified through phonon analysis, differing from previously proposed symmetries.

Contribution

The paper demonstrates that van der Waals corrections are crucial for accurately determining the stable crystal structure of AuSn₄, identifying a new stable phase with implications for topological properties.

Findings

AuSn₄ can be dynamically unstable with Aea2 and Ccca symmetries.

A stable Pc structure has lower energy than Aea2 or Ccca.

The stable structure is consistent with ARPES measurements.

Abstract

AuSn$_{4}$ is the example of an compound that exhibits topological properties. Recent XRD measurements reveal an ambiguous nature of the crystal structure, as it can be realized with either Aea2 or Ccca symmetry. Motivated by this, we analyze the dynamical stability of the compound. We discuss the role of van der Waals (vdW) corrections within the ab initio calculation. Interestingly, our main result indicates that AuSn$_{4}$ can be unstable with both Aea2 and Ccca symmetries, due to the soft modes in the phonon spectra. From the soft mode analyses we find dynamically stable Pc structure. This structure has always smaller energy than Aea2 or Ccca crystal and it stays independent of the vdW correction. We also show that the comparison of theoretical electronic properties with the experimental ARPES measurements. Our findings may be valuable in the future investigations of AuSn$_{4}$-like compounds.