Interatomic potential for the Al-Cu system

An angular-dependent interatomic potential has been developed for the Al-Cu system based on existing embedded-atom method potentials for Al and Cu and fitting of the cross-interaction functions to experimental and first-principles data. The potential reproduces lattice parameters, formation energies, and elastic constants of the $\ensuremath{\theta}$ and ${\ensuremath{\theta}}^{\ensuremath{'}}$ phases of this system. It predicts the ${\ensuremath{\theta}}^{\ensuremath{'}}$ phase to be more stable than $\ensuremath{\theta}$ at 0 K but to become less stable at hight temperatures due to vibrational entropy. The temperate and entropy of this phase transformation are in good agreement with previous first-principles calculations [C. Wolverton and V. Ozoli\ifmmode \mbox{\c{n}}\else \c{n}\fi{}\ifmmode \check{s}\else \v{s}\fi{}, Phys. Rev. Lett. 86, 5518 (2001)]. The potential provides a reasonable description of the phase stability across the Al-Cu phase diagram, dilute heats of solution, and other thermodynamic properties. It has also been tested for generalized stacking fault energies in the presence of a copper layer embedded in Al. This configuration bears some resemblance to Guinier-Preston zones that strengthen Al-Cu alloys. The trends predicted by the potential for uniform shearing of this configuration are in agreement with results of first-principles density-functional calculations performed in this work. The potential is expected to be suitable for atomistic simulations of precipitation hardening of Al-Cu alloys.