Dear LAMMPS mailing list,
I would like to setup a simulation with a few different small molecules (mixed) in the gas phase to simulation various properties, e.g. EOS. I would like to use point charges for each species with the exp-6 potential and a set of mixing rules for unlike species.
After consulting the manual, I’m not sure whether pair_style exp6/rx is appropriate for this? I would be very grateful if you could suggest some basic commands with which this can be achieved.
Best Regards,
Magnus
Dear LAMMPS mailing list,
I would like to setup a simulation with a few different small molecules (mixed) in the gas phase to simulation various properties, e.g. EOS. I would like to use point charges for each species with the exp-6 potential and a set of mixing rules for unlike species.
I doubt that any of the mixing rules implemented in LAMMPS applies to that. They are primarily meant to be used for Lennard-Jones type interactions.
Whether a pair style supports mixing should be mentioned in a section of its documentation. Typically, you would look up the necessary mixing rules in the publication where you obtain the suitable parameters for your atom types, and then specify all pair_coeff statements for all pairs of atom types.
After consulting the manual, I’m not sure whether pair_style exp6/rx is appropriate for this?
That is very unlikely, since that specific pair style is implemented for “reactive DPD” simulations and dependent on other features in the USER-DPD package.
I would be very grateful if you could suggest some basic commands with which this can be achieved.
If you cannot find a suitable pair style that implements the specific functional form you needs and your model is a pairwise additive potential, then you can represent it with either pair style python (convenient for prototyping, but quite slow) or pair style table (quite efficient, but a bit tricky to get to work well. we usually recommend to experiment with the pair style first by trying to reproduce calculations with a pair style for which an analytic version exists, e.g. lj/cut or morse, but it is also very convenient to create tables from pair style python and thus speed up such calculations. there are example inputs for that included with LAMMPS.
you can easily add coulomb interactions to pair styles by using pair style hybrid/overlay. that gives you access to a wide variety of cutoff, damped, and long-range solver compatible coulomb models.
HTH,
axel.