Modified embedded-atom method interatomic potentials for the $\mathrm{Mg}\text{−}\mathrm{Al}$ alloy system

We developed modified embedded-atom method (MEAM) interatomic potentials for the $\mathrm{Mg}\text{−}\mathrm{Al}$ alloy system using a first-principles method based on density functional theory (DFT). The materials parameters, such as the cohesive energy, equilibrium atomic volume, and bulk modulus, were used to determine the MEAM parameters. Face-centered cubic, hexagonal close packed, and cubic rock salt structures were used as the reference structures for Al, Mg, and $\mathrm{MgAl}$, respectively. The applicability of these MEAM potentials to atomistic simulations for investigating $\mathrm{Mg}\text{−}\mathrm{Al}$ alloys was demonstrated by performing simulations on Mg and Al atoms in a variety of geometries. These MEAM potentials were used to calculate the adsorption energies of Al and Mg atoms on $\mathrm{Al}\left(111\right)$ and $\mathrm{Mg}\left(0001\right)$ surfaces. The formation energies and geometries of various point defects, such as vacancies, interstitial defects, and substitutional defects, were also calculated. We found that the MEAM potentials give a better overall agreement with DFT calculations and experiments when compared against the previously published MEAM potentials.

Figure 1

Atomic energies (total energies per atom) as a function of the atomic volume (volume per atom) for Al atoms in fcc, hcp, bcc, and simple cubic (sc) crystal structures. The energies are measured from the equilibrium atomic energy of fcc structure. Volumes are scaled by the equilibrium atomic volume of the fcc structure $V_0^{\mathrm{fcc}}$.

Figure 2

Atomic energies of Mg as a function of the atomic volume in fcc, hcp, and bcc cubic crystal structures. The energies are measured from the equilibrium atomic energy of the hcp structure. Volumes are scaled by the equilibrium atomic volume of the hcp structure $V_0^{\mathrm{hcp}}$.

Figure 3

The heat of formation per atom for $\mathrm{MgAl}$ alloys in the $B1$, $B2$, and $B3$ crystal structures.

Figure 4

The heat of formation per atom for $\mathrm{Mg}\text{−}\mathrm{Al}$ alloys in various intermetallic phases with different stoichiometric coefficients. The results obtained from the $\mathrm{Mg}\text{−}\mathrm{Al}$ MEAM potentials are compared with the DFT calculations. The structure names are written next to the symbols (open triangles for DFT and crosses for MEAM).