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.

Effect of surface roughness on elastic limit of silicon nanowires

“…As an alternative way, molecular dynamics simulation can be performed to uncover the detailed deformation mechanism that experiments cannot capture. The Modified Embedded Atom Method (MEAM) potential [25] developed by Timonova and Thijsse (2011) was used to account for the interactions among silicon atoms. This potential was well fitted to cohesive energy, equilibrium lattice, bulk modulus, surface energy, cubic elastic constants, vacancy formation energy, and screw dislocation Peierls stress.…”

Modeling diffusion and phase transitions by a uniform-acceptance force-bias Monte Carlo method

“…9 show the results of this treatment for two temperatures, 506 and 2530 K. It can be seen that in both cases, the RDFs are surprisingly similar to the MD liquid. Although the coordination numbers are a little different,5.35 at 506 K and 5.27 at 2530 K versus 5.65 for MD, 7 it is safe to say that a too high value of ⌬ / 2 lets UFMC+ produce a liquid under conditions where the crystalline phase is thermodynamically stable.…”

“…This density corresponds with the experimental value at 0 K. Si-Si interactions were described with a recent parameterization of the modified embedded atom method potential, called MEAM-L. With the exception of the too high melting temperature ͑2990 K͒, this potential describes silicon properties better that many other potentials. 6,7 All UFMC and MD simulations were done at constant volume unless ͑for MD͒ indicated otherwise.…”

“…In a sense, this situation is similar to MD with a ten times higher heating rate ͑9.1 K/ps͒ than used here, for which also no crystallization was observed. 7 There seem to be simply not enough mobility for crystallization. Apparently the small value ⌬ / 2 = 0.06R eq prevents crystallization by holding atoms too closely near their positions in the amorphous phase, and the other UFMC parameter T cannot change this, even while at low-T atoms move over longer distances and while at high-T atoms move more often in the direction opposite to the force and could be expected to cross the energy barrier between the amorphous and crystal phases.…”

Improved method of calculatingab initiohigh-temperature thermodynamic properties with application to ZrC

“…MEAM potentials have been derived and applied to various elements and alloys encompassing a wide range of bonding characteristics [18,19]. In the present work, the reference-free formulation of the MEAM [20] is used as it removes the need to specify a reference structure, which otherwise restricts the form that the pair potentials can take. This enables greater variational freedom in the fitting of energies and atomic forces.…”