Comparison of semi-empirical potential functions for silicon and germanium

We report the results of investigations into the behavior of the crystalline and liquid phases of silicon and germanium as they are modeled by the Tersoff and modified-embedded-atom-method (MEAM) potentials. The structure of the solid-liquid interface produced by each potential is determined, as are the melting points corresponding to each potential model. The equilibrium properties of both crystalline and liquid silicon and germanium as modeled by the Tersoff and MEAM potentials are then presented. The Tersoff potential is found to overestimate greatly the melting point of both silicon and germanium, while the MEAM underestimates the melting point of silicon by approximately 15%. The MEAM does not yield a stable liquid phase of germanium. Both potential models produce a (100) solid-liquid interface for both semiconductors that is rough, while the (111) interface is found to be atomically smooth. The Tersoff potential yields an amorphous phase for both silicon and germanium, but efforts to produce an amorphous MEAM phase were unsuccessful. Rapid solidification of MEAM silicon produced unphysical regrowth velocities.