Electrical discharge triggers quasicrystal formation in an eolian dune

Significance

The article presents the quasicrystal created by an electrical discharge, in this case accidentally created by a lightning strike or a downed power line in a wind-created dune in the Sand Hills of north central Nebraska. The discharge produced extreme temperatures (>1,710 °C) that led to the formation of a fulgurite, a tube of fused and melted sand along with traces of melted conductor metal from the power line. Within the fulgurite was found a “dodecagonal quasicrystal” composed of equally spaced atomic layers, each with 12-fold symmetry and quasicrystalline order that is impossible for ordinary crystals. The discovery suggests mechanisms for forming quasicrystals in nature (on Earth and in space) and in the laboratory.

Abstract

We report the discovery of a dodecagonal quasicrystal Mn _72.3Si _15.6Cr _9.7Al _1.8Ni _0.6—composed of a periodic stacking of atomic planes with quasiperiodic translational order and 12-fold symmetry along the two directions perpendicular to the planes—accidentally formed by an electrical discharge event in an eolian dune in the Sand Hills near Hyannis, Nebraska, United States. The quasicrystal, coexisting with a cubic crystalline phase with composition Mn _68.9Si _19.9Ni _7.6Cr _2.2Al _1.4, was found in a fulgurite consisting predominantly of fused and melted sand along with traces of melted conductor metal from a nearby downed power line. The fulgurite may have been created by a lightning strike that combined sand with material from downed power line or from electrical discharges from the downed power line alone. Extreme temperatures of at least 1,710 °C were reached, as indicated by the presence of SiO ₂ glass in the sample. The dodecagonal quasicrystal is an example of a quasicrystal of any kind formed by electrical discharge, suggesting other places to search for quasicrystals on Earth or in space and for synthesizing them in the laboratory.