Au–Ge MEAM potential fitted to the binary phase diagram

Abstract

We have developed a modified embedded atom method potential for the gold–germanium (Au–Ge) binary system that is fitted to the experimental binary phase diagram. The phase diagram is obtained from the common tangent construction of the free energy curves calculated by the adiabatic switching method. While maintaining the accuracy of the melting points of pure Au and Ge, this potential reproduces the eutectic temperature, eutectic composition and the solubility of Ge in solid Au, all in good agreement with the experimental values. To demonstrate the self-consistency of the potential, we performed benchmark molecular dynamics simulations of Ge crystal growth and etching in contact with a Au–Ge liquid alloy.

Addressing the discrepancy of finding the equilibrium melting point of silicon using molecular dynamics simulations

“…Again, the Gibbs free energy for the liquid phase G L as a function of temperature between 1200 K and 1500 K was calculated using the reversible scaling method [38]. In the end, both G S and G L were plotted as a function of temperature T on the same scale and the melting temperature was determined as the intersection of the two curves [39,40]. Figure 4 shows the Gibbs free energy per atom of both the solid phase and the liquid phase for two different supercells.…”

Revealing Atomistic Mechanisms of Gold-Catalyzed Germanium Growth Using Molecular Dynamics Simulations

“…According to the liquidus of the Au–Ge phase diagram predicted by the adopted MEAM potential, we first constructed 16 configurations: four common crystallographic orientations of Ge solid substrates ({100}, {110}, {111}, and {112}), combined with four Ge equilibrium concentrations, corresponding to temperatures of 800, 850, 900, and 950 K, respectively. It should be noted that due to the time scale limitation of molecular dynamics, the simulation temperatures have to be set significantly higher than the typical experimental values, , to achieve observable growth of Ge atoms. , Then, by substituting different amounts of Au atoms in liquid, three additional Ge supersaturation conditions were created.…”

“…Growth. All of the MD simulations were carried out by the large-scale atomic/ molecular massively parallel simulator (LAMMPS) 34 using the MEAM potential 33 for the Au−Ge binary system. To ensure the comparability among configurations with different crystallographic orientations of Ge substrates, we controlled the size of the simulation cell to be similar to each other.…”

“…This motivates us to adopt the molecular dynamics (MD) method to study the VLS mechanisms of the Au–Ge system, considering that MD simulations have been used for similar VLS systems such as Au-catalyzed silicon growth. − It should be noted that one general difficulty in the classical MD approach is the availability of an accurate interatomic potential for the target system . In this regard, we have developed an MEAM potential for the Au–Ge system that was well fitted to the binary phase diagram, as an enabler of the systematic investigations in this study. Here, we performed MD simulations of Au-catalyzed Ge crystal growth on four common Ge substrate orientations in a range of temperature ( T ) and Ge supersaturation (Δ x Ge ) conditions.…”

Identifying interatomic potentials for the accurate modeling of interfacial segregation and structural transitions

“…In some cases, the relevant material properties or defects energies of interest are obvious. For example, a direct fit to anisotropic elastic moduli can be used if elasticity is of interest [21], while fitting to the experimental phase diagram will allow precipitation and phase separation to be modeled [22]. In other cases, it is more difficult to isolate the essential properties to be fit for accurate simulation, particularly when a given phenomenon is not directly related to an equilibrium thermodynamic parameter in the bulk.…”