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Finite temperature molecular dynamics study of unstable stacking fault free energies in silicon
We calculate the free energies of unstable stacking fault (USF)
configurations on the glide and shuffle slip planes in silicon as a function of
temperature, using the recently developed Environment Dependent Interatomic
Potential (EDIP). We employ the molecular dynamics (MD) adiabatic switching
method with appropriate periodic boundary conditions and restrictions to atomic
motion that guarantee stability and include volume relaxation of the USF
configurations perpendicular to the slip plane. Our MD results using the EDIP
model agree fairly well with earlier first-principles estimates for the
transition from shuffle to glide plane dominance as a function of temperature.
We use these results to make contact to brittle-ductile transition models.Comment: 6 pages revtex, 4 figs, 16 refs, to appear in Phys. Rev.
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Comparison between classical potentials and ab initio for silicon under large shear
The homogeneous shear of the {111} planes along the direction of bulk
silicon has been investigated using ab initio techniques, to better understand
the strain properties of both shuffle and glide set planes. Similar
calculations have been done with three empirical potentials, Stillinger-Weber,
Tersoff and EDIP, in order to find the one giving the best results under large
shear strains. The generalized stacking fault energies have also been
calculated with these potentials to complement this study. It turns out that
the Stillinger-Weber potential better reproduces the ab initio results, for the
smoothness and the amplitude of the energy variation as well as the
localization of shear in the shuffle set
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