The uniform-acceptance force-bias Monte Carlo ͑UFMC͒ method ͓G. Dereli, Mol. Simul. 8, 351 ͑1992͔͒ is a little-used atomistic simulation method that has strong potential as alternative or complementary technique to molecular dynamics ͑MD͒. We have applied UFMC to surface diffusion, amorphization, melting, glass transition, and crystallization, mainly of silicon. The purpose is to study the potential and the limitations of the method: to investigate its applicability, determine safe and effective values of the two UFMC parameters-a temperature and a maximum allowed atomic displacement per iteration step-that lead to reliable results for different types of simulations, assess the computational speed increase relative to MD, discover the microscopic mechanisms that make UFMC work, and show in what kind of simulations it can be useful and preferable over MD. It is found that in many simulations, UFMC can be a very efficient alternative to MD: it leads to analogous results in much fewer iteration steps. Due to the straightforward formalism of UFMC, it can be easily implemented in any MD code. Thus both methods can be combined and applied in turn, using UFMC for the acceleration of certain processes and MD for keeping precision and monitoring individual atom trajectories.

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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.

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