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[lammps-users] Transition from EEM to QEq when implementing ReaxFF in LAMMPS
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[lammps-users] Transition from EEM to QEq when implementing ReaxFF in LAMMPS

From: Georg Heinze <georg.heinze@...6617...>
Date: Thu, 15 Jun 2017 14:12:08 +0200

Dear all,

I am currently simulating the oxidation of silicon nanowires using ReaxFF with Parameters by Buehler et al. (Phys. Rev. Lett. 96, 2006) in LAMMPS. My first approach is to replicate calculations by Khalilov et al. (Nanoscale 5, 2013) carried out using the Reax Code. When comparing my data to the data obtained by Khalilov et al. I noticed a difference that is most likely related to charges. Charge equalization in LAMMPS is realized via QEq while in the Reax Code it is realized via EEM. In the original QEq paper by Rappe and Goddard (J. Phys. Chem. 95, 1991) it is mentioned that the charges obtained via EEM are a factor 3-6 small in comparison to charges obtained via QEq. In the original ReaxFF paper by van Duin et al. (J. Phys. Chem. A 105, 2001) it is argued that QEq and EEM are very similar and that the main difference between the two can be compensated by adjusting a shielding parameter in the Coulomb Term of ReaxFF. The question I have is whether and how the difference between QEq and EEM was considered when ReaxFF was implemented in LAMMPS.

Kind regards,
Georg Heinze