Angular-dependent embedded atom method potential for atomistic simulations of metal-covalent systems

A computationally efficient interatomic potential is developed for the description of interatomic interactions in multicomponent systems composed of metals, Si and Ge. The potential is based on reformulation of the embedded atom method (EAM) potential for metals and Stillinger-Weber (SW) potential commonly used for Si and Ge in a compatible functional form. The potential incorporates a description of the angular dependence of interatomic interactions into the framework of the EAM potential and, therefore, is dubbed angular-dependent EAM (A-EAM) potential. The A-EAM potential retains the properties of the pure components predicted by the original EAM and SW potentials, thus limiting the scope of potential parameterization to only the cross interactions among the components. The ability of the potential to provide an adequate description of binary systems with mixed type of bonding is illustrated for Au-Si/Ge system, with the parameters for Au-Si and Au-Ge interactions determined based on the results of density-functional theory calculations performed for several representative bulk structures and small clusters. To test the performance of the A-EAM potential at finite temperatures, the values of the enthalpy of mixing of liquid Au-Si and Au-Ge alloys, as well as the equilibrium lines on the Au-Si phase diagram are evaluated and compared with experimental data. The calculation of the phase diagram is based on the values of the excess chemical potential difference between Au and Si, evaluated in a series of semi-grand canonical ensemble Monte Carlo simulations performed for different temperatures and alloy compositions. The potential is shown to provide an adequate semiquantitative description of the thermodynamic properties of the alloy at different temperatures and in the whole range of compositions, thus showing a considerable promise for large-scale atomistic simulations of metal-Si/Ge systems.