Spontaneously formed quasicrystal grains in a pure metal

Zhengming Wang,Donghua Xu,Tzu-Yi Chang

doi:10.1063/5.0032991

Abstract

Pure metals so far have been obtained in quasicrystal (QC) forms only by templation – epitaxial growth on a QC substrate. Here, we report spontaneous formation of dodecagonal QC (DDQC) grains in pure tantalum (Ta), an early transition metal normally in a body-centered-cubic crystal structure. The DDQC grains comprise icosahedral clusters assembled in accordance with the Stampfli triangle–square tiling scheme and are formed directly from the supercooled liquid and the β-Ta phases during thermal devitrification of a Ta metallic glass in molecular dynamics simulations using a realistic quantum mechanically based interatomic potential. They co-exist with β-Ta and are retainable to and stable at room temperature, with a slightly lower configurational energy than β-Ta.

Highlights

Since the Nobel prize-winning discovery of the first of the kind by Shechtman et al.,1 quasicrystals (QCs) with rotational but no translational symmetry have been attracting tremendous interest from various disciplines, e.g., materials science, physics, chemistry, and mathematics
The β-Ta crystal structure belongs to the σ-phase among the Frank–Kasper topologically close pack (TCP) crystal structures
We have discovered that dodecagonal QC (DDQC) grains with a 12-fold symmetry are formed spontaneously from the supercooled liquid and β-Ta phases upon thermal devitrification of a pure Ta metallic glass, without a template

Summary

INTRODUCTION

Since the Nobel prize-winning discovery of the first of the kind by Shechtman et al., quasicrystals (QCs) with rotational but no translational symmetry (in at least one dimension) have been attracting tremendous interest from various disciplines, e.g., materials science, physics, chemistry, and mathematics. The thickness of the templated pure-metal QC films is typically limited to one to a few tens of atomic layers beyond which the QC structure is lost. Our recent simulations of pure metals using realistic quantum mechanically based embedded-atom-method (EAM) potentials uncovered that BCC (body-centered-cubic) metals generally possess higher. We will show that Ta can even form DDQC grains spontaneously under a simple thermal condition – isothermal annealing of an MG (above the peak-nucleationrate temperature regime for the equilibrium crystal), and we will present the atomic structure, tiling scheme, formation mechanisms, and energy state of the first spontaneously formed QC in a pure metal

SIMULATION DETAILS

RESULTS AND DISCUSSION

CONCLUSION