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Formation of a single quasicrystal upon collision of multiple grains

Abstract Quasicrystals exhibit long-range order but lack translational symmetry. When grown as single crystals, they possess distinctive and unusual properties owing to the absence of grain boundaries. Unfortunately, conventional methods such as bulk crystal growth or thin film deposition only allow us to synthesize either polycrystalline quasicrystals or quasicrystals that are at most a few centimeters in size. Here, we reveal through real-time and 3D imaging the formation of a single decagonal quasicrystal arising from a hard collision between multiple growing quasicrystals in an Al-Co-Ni liquid. Through corresponding molecular dynamics simulations, we examine the underlying kinetics of quasicrystal coalescence and investigate the effects of initial misorientation between the growing quasicrystalline grains on the formation of grain boundaries. At small misorientation, coalescence occurs following rigid rotation that is facilitated by phasons. Our joint experimental-computational discovery paves the way toward fabrication of single, large-scale quasicrystals for novel applications.

36 MATERIALS SCIENCE↗

Materials Data on AlCo2Ni by Materials Project

Co2NiAl is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Co is bonded in a distorted body-centered cubic geometry to four equivalent Ni and four equivalent Al atoms. All Co–Ni bond lengths are 2.45 Å. All Co–Al bond lengths are 2.45 Å. Ni is bonded in a 8-coordinate geometry to eight equivalent Co and six equivalent Al atoms. All Ni–Al bond lengths are 2.83 Å. Al is bonded in a distorted body-centered cubic geometry to eight equivalent Co and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗

Materials Data on Al9Co2Ni by Materials Project

Co2NiAl9 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are three inequivalent Co sites. In the first Co site, Co is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Co–Al bond distances ranging from 2.37–2.52 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Co–Al bond distances ranging from 2.35–2.61 Å. In the third Co site, Co is bonded in a 10-coordinate geometry to ten Al atoms. There are a spread of Co–Al bond distances ranging from 2.50–2.63 Å. Ni is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Ni–Al bond distances ranging from 2.32–2.63 Å. There are ten inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to four Co atoms. In the second Al site, Al is bonded in a 3-coordinate geometry to three Co and three Al atoms. There are one shorter (2.50 Å) and two longer (2.64 Å) Al–Al bond lengths. In the third Al site, Al is bonded in a 3-coordinate geometry to one Co, two equivalent Ni, and one Al atom. The Al–Al bond length is 2.83 Å. In the fourth Al site, Al is bonded in a bent 150 degrees geometry to two equivalent Ni atoms. In the fifth Al site, Al is bonded in a 4-coordinate geometry to three Co, one Ni, and seven Al atoms. All Al–Al bond lengths are 2.67 Å. In the sixth Al site, Al is bonded in a 3-coordinate geometry to two equivalent Co, one Ni, and one Al atom. The Al–Al bond length is 2.88 Å. In the seventh Al site, Al is bonded in a linear geometry to two equivalent Co atoms. In the eighth Al site, Al is bonded in a 3-coordinate geometry to two Co, one Ni, and one Al atom. In the ninth Al site, Al is bonded in a 3-coordinate geometry to three Co atoms. In the tenth Al site, Al is bonded in a 12-coordinate geometry to four equivalent Co and eight Al atoms.

36 MATERIALS SCIENCE↗