Hello everyone,
I have been doing simulations of atomic insertions in the GCMC ensemble using REAXFF parameters for CO2. The pair style commands I have been using
pair_style hybrid/overlay lj/cut 2.5 reaxff NULL safezone 3.0 mincap 150
pair_coeff * * reaxff ffield.reax.cho C O
pair_coeff 1 1 lj/cut 0.053649 2.8
pair_coeff 2 2 lj/cut 0.156973 3.05
bond_coeff 1 46.121 1.17
angle_coeff 1 2.0918 180
When this command is not added
fix mygcmc co2 gcmc 100 100 0 0 9869 300 0 1 pressure 1 region co2 mol co2mol
The program works well. However, when this command is added. The number of CO2 in simulation region keeps increasing without limitation.
I would like to know how to fix it.
This cannot be correct.
- for C-C and O-O interactions you are adding the Lennard-Jones interaction on top of the ReaxFF
- Your LJ cutoff of 2.5 is shorter than the LJ sigma, i.e. it only applies somewhere high on the repulsive branch. That is certainly bogus.
- Why would one use ReaxFF for this kind of system in the first place? Why not a conventional CO2 model using a conventional molecular force field and fix rigid?
Outside of the bad interaction model that you have, the next problem are the choices for the GCMC parameters that matter. Most importantly the chemical potential (which you set indirectly though the pressure). There is a whole lot of theory attached to this. Far more than what can be repeated here.
Thanks for your reply. I would like to simulate the adsorption of CO2 under electric field. I used conventional CO2 model with lj/cut/coul/long force field to simulate the adsorption of CO2 without electric field successfully. But I have no idea how to show the effect of electric filed on adsorption. Do you have any suggestion?
Check out the published literature. That is a better source for this kind of knowledge.
Please note that this is not really a LAMMPS problem, but a question of how to do research and that is a discussion you should have with people that know and care about your research, like your adviser or supervisor or colleagues or collaborators. After all, it would look rather strange when you write in your paper “some random dude on the internet told me to do this”.
You should probably also check out this recent discussion: Using electric field in reaxff period boundary
