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

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.