Implementation of a Modified Stillinger-Weber for SiO2 found in the literaure (Smirnov 2005)

Hello all,

I was hoping to implement a modified version of the Stillinger-Weber potential for silicon dioxide found in the following paper (Molecular-dynamics model of energetic fluorocarbon-ion bombardment on SiO2 I. Basic model and CF2+-ion etch characterization | Journal of Applied Physics | AIP Publishing). The angle-term in the 3-body interaction is a little different than the implementation in LAMMPS, so I was hoping to use the pair_style sw/angle/table command to account for this flexibility. However, it appears that there is another complicating factor. The gamma terms in the aforementioned paper are defined for pairs of atoms within a given triplet, while in LAMMPS the gamma terms are defined for pairs of atoms regardless of the triplet they belong to. For example, in the Smirnov paper, the gamma for an Si-Si interaction within a Si-Si-Si triplet is different than the gamma for an Si-Si interaction within a Si-Si-O triplet. Whether or not this even makes sense is a another question, but I would like to look into this potential regardless.
But my question is whether or not LAMMPS has the flexibility to handle this. Given the way pair potential parameters are read in for the Stillinger-Weber pair_style (I believe redundant parameters are ignored) I’m guessing LAMMPS can’t do this with the pair_style sw/angle/table command. Please let me know if I am wrong or if there is a work around for this.

LAMMPS does what the documentation say it does. If you are uncertain about specific details, it is recommended that you set up a suitable minimal test input, ideally with just a few atoms, so you can confirm the results from manual computations.

If you want something else than what is implemented, you’ll have to create a modified version of the corresponding C++ class(es). Please see: 3. Modifying & extending LAMMPS — LAMMPS documentation