Stability of atomic structures in the Al-Co-Cu quasicrystal phase

We perform replica-exchange Monte Carlo/molecular dynamics simulations that allow swapping between different chemical species in large crystalline approximants in order to discover optimal atomic configurations. We fit density functional theory energies and forces to empirical oscillating pair potentials (EOPP) which are characterized by short-range repulsion and long-range Friedel oscillations. We perform a series of simulations for the AlCoCu quasicrystal at various compositions and densities with temperatures ranging from room temperature to beyond the melt point. Among these resulting low energy structures, we observe ten-fold symmetry and we are able to distinguish particular tiling patterns when connecting transition metal bonds. We further carry out density functional energy calculation and confirm our best structure to be only 9meV/atom above the convex hull, suggesting the AlCoCu quasicrystal phase may be entropically stabilized at elevated temperatures.