First experimental synthesis of Al$_{\mathrm{62}}$Cu$_{\mathrm{31}}$Fe$_{\mathrm{7}}$ icosahedral quasicrystals and their natural origin in a meteorite by impact processes*

Quasicrystals (QCs) produced by shock recovery experiments shine light on the impact origin of natural QCs in the Khatyrka meteorite [1,2]. Al$_{\mathrm{62}}$Cu$_{\mathrm{31}}$Fe$_{\mathrm{7}}$ i-phase II is a newly found natural QC that has not previously been synthesized in the laboratory [3]. The compositions of Al-Cu-Fe QCs synthesized by shock have so far been similar but not identical to natural icosahedrite (Al$_{\mathrm{63}}$Cu$_{\mathrm{24}}$Fe$_{\mathrm{13}})$ and i-Al$_{\mathrm{62}}$Cu$_{\mathrm{31}}$Fe$_{\mathrm{7}}$ [3]. Here we present the results of a new shock recovery experiment using a compositionally graded Al-Cu-W wedge in a SS304 chamber. Surprisingly, the Al-rich region did not produce QCs whereas the intermediate Al-Cu mixture reacted with the steel chamber to generate i-Al$_{\mathrm{62}}$Cu$_{\mathrm{30}}$Fe$_{\mathrm{7}}$Cr$_{\mathrm{1}}$, co-existing with Al$_{\mathrm{2}}$Cu (khatyrkite) and Al$_{\mathrm{3}}$Cu$_{\mathrm{2}}$ (stolperite) alloys. Conceivably, this results from the effects of shear flow during shock that stabilizes the new composition of icosahedral QC. More importantly, the synthesized i-phase II is a near-exact compositional, textural and assemblage match to its natural occurrence in the Khatyrka meteorite. [1] Asimow, P.D. \textit{et al.} (2016) \textit{PNAS}, 113, 7077. [2] Oppenheim, J. \textit{et al.} (2017) \textit{Sci. Rep.}, 7, 15629. [3] Bindi, L. \textit{et al.} (2016) \textit{Sci. Rep.}, 6, 38117.