Optimizing the MEAM potential for silicon

Abstract

By applying simulated annealing techniques we fit the modified embedded atom method (MEAM) potential to a database of ab initio energies for silicon and construct an improved parametrization of this potential. In addition, we introduce a new, reference-free version of the MEAM potential. This MEAM version is also fitted to the silicon data and shows an even better agreement, although the improvement is modest. Finally, we investigate whether increasing the number of different angular terms in the MEAM potential from 3 to 4 will lead to a better potential. The aim of this work is to determine a broad-ranged potential, one that is reliable in many different low- and high-energy atomic geometries in silicon crystals, molecules, near defects and under strain. To verify this, the performance of the new potentials is tested in different circumstances that were not explicitly included in the fit: relaxed defect energies, thermal expansion, melting temperature and liquid silicon. The new MEAM parametrizations found in this work, called MEAM-M and RF-MEAM, are shown to be overall more accurate than previous potentials—although a few defect energies are exceptions—and we recommend them for future work. The melting temperatures are closer to the experiment than those of other MEAM potentials, but they are still too high.