Empirical potential-based Si-Ge interatomic potential and its application to superlattice stability.

Abstract

A new empirical interatomic potential for Si-Ge alloy system is proposed based on the Khor--Das Sarma universal interatomic potential for tetrahedrally bonded materials. We modify the Khor--Das Sarma potential and check its validity by calculating the elastic constants of Si and Ge using the homogeneous-deformation method. The feasibility for applying this potential to binary systems is tested by investigating pressure-induced phase transitions associated with isotropic compression and tetragonal distortion. The new empirical potentials for Si, Ge, and Si-Ge are used to calculate thermodynamic properties such as lattice parameters, bond lengths, and excess energies for Si-Ge superlattices. The calculated results are shown to be in good agreement with available experimental data. We also calculate the phonon dispersion for bulk Si. The newly obtained empirical potentials for Si, Ge, and Si-Ge should be useful for investigating Si-Ge binary systems.