| Abstract Scope |
The discovery of quasicrystals forced solid-state chemists to revisit basic assumptions about crystallinity, bonding, and materials stability. A fundamental question emerged: Are quasicrystals thermodynamically stable? Or are quasicrystals metastable but nucleation-preferenced due to a low surface energy? Density functional theory is often used to evaluate thermodynamic stability, but quasicrystals are aperiodic and cannot be simulated using periodic boundary conditions. Here, we present a new technique to directly calculate the bulk and surface energies of quasicrystals in DFT. We compute the energies of quasicrystal nanoparticles with increasing sizes, and then fit the bulk and surface energies of the nanoparticles using a Gibbs-Thomson relationship. Using this technique, we evaluate the Tsai-type ScZn and YbCd icosehdral quasicrystals, whose structures have been resolved with atomistic resolution. From the bulk and surface energies, we construct size-dependent phase diagrams along with quasicrystal Wulff shapes, enabling us to establish the bulk and nanoscale (meta)stability of icosahedral quasicrystals. |