I want to simulate water and graphene system, can i use the hybrid airebo tip3 firec field for my system.
Regards
Javeed
Using a many-body pair_style like AIREBO can be a headache. Instead, for graphene, I have seen people treat the carbon atoms as aromatic carbons. Then they use the aromatic carbon type from a simple popular force field such as OPLSAA or AMBER(GAFF,GAFF2). Here is an example of somebody who uses this approach:
https://github.com/velocirobbie/make-graphitic
He uses the OPLSAA aromatic carbon .(This is @atom type #90 from the “oplsaa.prm”/“oplsaa.lt” files.) But I reallydon’t know if this is a good strategy.
It is probably more accurate to use AIREBO to describe the interaction between the graphene carbon atoms, but it is a lot of work to convert the force field parameters from eV into kcal/mol and visa-versa. (I have never tried doing that.) Ultimately I don’t think it matters that much if you are using a realistic force field for the carbon atoms in the graphene sheet, unless you expect it to bend and change shape significantly. Small graphene sheets are probably relatively stiff. (So in my example, I actually make the entire graphene sheet rigid. Laurent Joly also did this as well in his 2011 paper.)
As for the interaction between the carbon atoms and the water, you can try using these Lennard-Jones parameters
For the interaction between the graphene carbon and water oxygen, use:
epsilon = 0.114 kcal/mol, sigma = 3.2 Angstroms
These parameters come from this paper:
Laurent Joly, J. Chem. Phys. 135(21):214705 (2011)
You can turn off the interaction between the graphene carbon and the water hydrogen, using
epsilon = 0.0 for that pair of atom types. (In that paper, he also makes the graphene sheets rigid.)
As for the water, I think any of these water models should be reasonable:
TIP3P, SPC/E, TIP4P, TIP5P
Good luck.
Andrew
[…]
Using a many-body pair_style like AIREBO can be a headache. Instead, for graphene, I have seen people treat the carbon atoms as aromatic carbons. Then they use the aromatic carbon type from a simple popular force field such as OPLSAA or AMBER(GAFF,GAFF2).
Regardless of whether one uses a manybody potential for the graphene atoms or not, one always has to provide the interactions between the graphene and the water with a pairwise-additive model and for those the method from above is what people do. Since most manybody potentials are parameterized in metal units while most molecular force fields use kcal/mol or kJ/mol, the force field parameters need to be converted, but that is usually straightforward since it is only the energy terms that usually need to be changed. For a few manybody potentials (e.g. tersoff, eam, sw) LAMMPS can now also rescale the parameters in the potential file from metal to real units when loading the potential file, provided the file contains a suitable units tag.