Dear lammps users,
I am trying to use the ReaxFF for Polypropylene. For polymer materials (only C and H), is it correct to use pair_coeff "ffield.reax.cho (Reactive MD-force field c/h/o combustion force field)" as follow:
pair_coeff * * ffield.reax.cho C C C H
For a system with:
4 atom types
Masses
1 12.01115 # c
2 12.01115 # c1
3 12.01115 # c=2
4 1.00797 # hc
The Syntax is correct, the force field file not.
Thanks, Axel. I modified it:
pair_coeff * * ffield.reax C C C H
In the case of using other packages for initial structure of polymer ( such Moltemplates, EMC and etc…), is it fundamentally correct to first equilibrium the structure with non-reactive FF (PCFF or opls) and then at the last step switch the force field to ReaxFF?
Thanks, Axel. I modified it:
pair_coeff * * ffield.reax C C C H
In the case of using other packages for initial structure of polymer ( such Moltemplates, EMC and etc…), is it fundamentally correct to first equilibrium the structure with non-reactive FF (PCFF or opls) and then at the last step switch the force field to ReaxFF?
it is correct, if it is done correctly. there are differences in the way how you have to assign atom types, the atom style required, and what topology information you need to provide.
for hydrocarbon compounds, you may also consider using AIREBO (even for the production simulation). the key element is to always use parameter sets and typing and topology data that is consistent with the forcefield and the material under the conditions that you are simulating.
this discussion has now moved completely away from anything related to LAMMPS and is about doing correct MD simulations in general (and independent of the MD code). that makes any followups off-topic and thus I recommend you discuss this with your adviser/supervisor or colleagues with experience in the field or a collaborator or a designated tutor. a mailing list is not a good place for this kind of tutoring/advising in the first place.
axel.