Hi,
There seems to be some variation in naming definitions for these potentials, but I would like to implement what I call the Brenner potential as presented by Brenner in Phys. Rev. B, 42 (1990), for carbon-carbon interactions. I found several similar entries in the mail list archives. It was suggested that implementing the AIREBO potential with the LJ and torsional terms turned off, yields the “REBO” or “Brenner” potential, depending on terminology used. From reading the description of the AIREBO potential in the LAMMPS documentation, my understanding is that turning off LJ and torsional terms will yield what I call the REBO potential, which is presented by Brenner in Journal of Physics Condensed Matter, 14 (2002). Therefore, I am interested in implementing a different version of the potential, which follows the functional form of the 1990 Brenner potential. It is mentioned several times that this is possible is someone submits this potential. So, here I am hoping someone has submitted a Brenner (1990) potential for LAMMPS implementation(?) If not, if someone could suggest the simplest way to modify the currently implemented REBO (2002) potential to return the original Brenner (1990) potential (if possible) I would appreciate it. Thanks!
Maybe Dave Schall can verify that AIREBO (as in LAMMPS) with
the 2 terms turned off is in fact the 2002 Brenner REBO. I didn't
think they were quite the same, but I think Dave said they were
recently.
Regarding the earlier Brenner potential, no one has worked on this
to my knowledge. There is no short-cut but to understand the
current AIREBO implementation and modify/replace it as necessary.
Steve
Yes, Airebo (Stuart, 2000) with the LJ and torsion off and 2nd generation REBO (Brenner 2002) are very similar, for all intents and purposes the same. And as Steve points out nobody has coded the 1st generation Brenner (1990). It would be a worthwhile endeavor because there are a number of other elements parameterized using its formalism. It would probably be easiest to start with Tersoff rather than Airebo if you are going to try to code it yourself. 1st gen REBO is most similar to the Tersoff family of potentials since it uses the same type expressions for the attractive and repulsive terms. That just leaves the bond order terms (nontrivial) to code.
Dave - just posted a 5Jun11 patch with a separate pair_style rebo
command. You can check the doc page to see if I have described
the AIREBO/REBO connection correctly - thanks for your input on this.
Steve