Seeking advice: RDF force field

[email protected]

Dears LAMMPS community,

Summary: I am running a simulation to replicate a previous simulation work has been done using different force field (DOI: They used COMPASS force field while I am using OPLSaa. The idea is to compare with their experimental and simulation result. I am getting some reasonable results however others are not making sense for me.

I run the equilibration stages using
1- NVE then NPT I took the box size (density and temperature were stable but pressure fluctuate ±1000 please see the summary below)
2- then use NVT (I was hoping to minimize the pressure fluctuation but it didn’t >> run it for 10K step just to make sure)
3- production stage: NVT and calculate the RDFs

I was able to get density (0.934g/cm3) close to the experimental density (0.94g/cm3). However, the RDF is not in agreement (i attached a picture showing the RDFs from my simulation OPLSaa left column vs COMPASS right side).

I checked my script and the atom assignments and the potentials (which is generated using Moltemplate). but couldn’t figure out and kind of get lost. I would be very thankful to give me advice about where and what to check is it a script? is it force field limitation? is this related to the pressure fluctuation? Or other aspects I am not taking into account?

Summary and part of the script is written bellow

Many thanks,
PhD student at university of Strathclyde

Picture rrdf.png

this is a discussion you need to have with your adviser/supervisor/senior colleagues.
you need to visualize your structures to see, if they look reasonable and you have to make test with small test systems to confirm that you are using your force fields correctly.
since this is all about how to do your research, neither of it is relevant to this mailing list. that you are using LAMMPS doesn’t matter.