LAMMPS Implementation of Streitz-Mintmire (CTIP) Variable Charge Potential

LAMMPS LAMMPS General Discussion
1

Hello LAMMPS Users,

I am looking to run some metal oxidation studies and am interested in using the Streitz-Mintmire (CTIP) potential form to handle the variable charges. I can see in the LAMMPS documentation that the original Streitz-Mintmire formalism has been implemented with the coul/streitz pair style. However, I would like to know if the valence charge bound corrections proposed by Zhou et al (Phys. Rev. B 69, 035402 (2004) - Modified charge transfer--embedded atom method potential for metal/metal oxide systems) have also been implemented? I do not see this anywhere in the documentation, but have seen it used in several recent publications making use of LAMMPS (for example: https://doi.org/10.1021/acs.chemmater.8b03969), and it is also referenced in the most recent LAMMPS publication (Redirecting). Any clarity on this issue would be appreciated.

Thanks,
Gabriel Plummer

2

I have sent an email to the developer of the coul/streitz pair style to provide his comments on that.
When I look at the potential files (AlO.streitz and AlO.eam.alloy) it seems they are consistent with what you are looking for. However, it also looks like the corrections proposed by Zhou only affect the EAM potential file not the pair style itself.

3

Thank you, Axel. My main concern from preliminary testing is that when I apply compressive isotropic strain to an Al2O3 cell, the charges on Al and O readily exceed +3 and -2 respectively (this occurs at only around 2% strain). Including the charge bound corrections of Zhou et al should not allow this to happen. Those corrections also require the definition of q(min) and q(max) for each atomic species and a coefficient, omega. For the coul/streitz pair style I do not see any place for the definition of these parameters, which made me think it had not been implemented.

4

That is definitely a question for the developer/contributor of the pair style. This sounds like it would be a feature that needs to be available in the charge-equilibration fix. Coincidentally, those fixes and the QEQ package were written by the same person. If you need his contact info please let me know.

5

Yes, that would be perfect if you would like to email me ([email protected]). Thanks!