Shock synthesis of quasicrystals with implications for their origin in asteroid collisions

• Published in: Proceedings of the National Academy of Sciences - PNAS 2016-06, Vol.113 (26), p.7077-7081
• Main Authors: Asimow, Paul D., Lin, Chaney, Bindi, Luca, Ma, Chi, Tschauner, Oliver, Hollister, Lincoln S., Steinhardt, Paul J.
• Format: Article
• Language: English
• Subjects: alloys; Crystals; High pressure; icosahedrite; meteorites; MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE; Physical Sciences; quasicrystals; shock metamorphism; Simulation; Stainless steel; Symmetry; Thermodynamics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1600321113

We designed a plate impact shock recovery experiment to simulate the starting materials and shock conditions associated with the only known natural quasicrystals, in the Khatyrka meteorite. At the boundaries among CuAl₅, (Mg0.75Fe2+ 0.25)₂SiO₄ olivine, and the stainless steel chamber walls, the recovered specimen contains numerous micron-scale grains of a quasicrystalline phase displaying face-centered icosahedral symmetry and low phason strain. The compositional range of the icosahedral phase is Al68–73Fe11–16Cu10–12Cr1–4Ni1–2 and extends toward higher Al/(Cu+Fe) and Fe/Cu ratios than those reported for natural icosahedrite or for any previously known synthetic quasicrystal in the Al-Cu-Fe system. The shock-induced synthesis demonstrated in this experiment reinforces the evidence that natural quasicrystals formed during a shock event but leaves open the question of whether this synthesis pathway is attributable to the expanded thermodynamic stability range of the quasicrystalline phase at high pressure, to a favorable kinetic pathway that exists under shock conditions, or to both thermodynamic and kinetic factors.