Light Localization in Local Isomorphism Classes of Quasicrystals.

We study a continuum of photonic quasicrystal heterostructures derived from local isomorphism (LI) classes of pentagonal quasicrystal tilings. These tilings are obtained by direct projection from a five-dimensional hypercubic lattice. We demonstrate that, with the sole exception of the Penrose LI class, all other LI classes result in degenerate, effectively localized states, with precisely predictable and tunable properties (frequencies, frequency splittings, and densities).

Evidence of cross-cutting and redox reaction in Khatyrka meteorite reveals metallic-Al minerals formed in outer space.

We report on a fragment of the quasicrystal-bearing CV3 carbonaceous chondrite Khatyrka recovered from fine-grained, clay-rich sediments in the Koryak Mountains, Chukotka (Russia). We show higher melting-point silicate glass cross-cutting lower melting-point Al-Cu-Fe alloys, as well as unambiguous evidence of a reduction-oxidation reaction history between Al-Cu-Fe alloys and silicate melt. The redox reactions involve reduction of FeO and SiO to Fe and Fe-Si metal, and oxidation of metallic Al to AlO, occurring where silicate melt was in contact with Al-Cu-Fe alloys.

Collisions in outer space produced an icosahedral phase in the Khatyrka meteorite never observed previously in the laboratory.

We report the first occurrence of an icosahedral quasicrystal with composition AlCuFe, outside the measured equilibrium stability field at standard pressure of the previously reported Al-Cu-Fe quasicrystal (AlCuFe, with x between 61 and 64, y between 24 and 26, z between 12 and 13%). The new icosahedral mineral formed naturally and was discovered in the Khatyrka meteorite, a recently described CV3 carbonaceous chondrite that experienced shock metamorphism, local melting (with conditions exceeding 5 GPa and 1,200 °C in some locations), and rapid cooling, all of which likely resulted from impact-induced shock in space. This is the first example of a quasicrystal composition discovered in nature prior to being synthesized in the laboratory.

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

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, (Mg0.75Fe(2+) 0.

Natural quasicrystal with decagonal symmetry.

We report the first occurrence of a natural quasicrystal with decagonal symmetry. The quasicrystal, with composition Al71Ni24Fe5, was discovered in the Khatyrka meteorite, a recently described CV3 carbonaceous chondrite. Icosahedrite, Al63Cu24Fe13, the first natural quasicrystal to be identified, was found in the same meteorite.

Impact-induced shock and the formation of natural quasicrystals in the early solar system.

The discovery of a natural quasicrystal, icosahedrite (Al63Cu24Fe13), accompanied by khatyrkite (CuAl2) and cupalite (CuAl) in the CV3 carbonaceous chondrite Khatyrka has posed a mystery as to what extraterrestrial processes led to the formation and preservation of these metal alloys. Here we present a range of evidence, including the discovery of high-pressure phases never observed before in a CV3 chondrite, indicating that an impact shock generated a heterogeneous distribution of pressures and temperatures in which some portions reached at least 5 GPa and 1,200 °C. The conditions were sufficient to melt Al-Cu-bearing minerals, which then rapidly solidified into icosahedrite and other Al-Cu metal phases.