How to obtain the coarse grain force field parameter

LAMMPS LAMMPS Beginners
1

Hello everyone, I am a beginner in LAMMPS , don,t know how to obtain the coarse grained force field parameter for ionic liquids. Please help.Thanks in advance

2

It depends on what you are looking for and you shld check the literature for these parameters.
What kind of force filed is used for the type of system that you want to simulate and things like this…

Best

3

Hello,

I dont think that LAMMPS has any functionality that allows you to derive classical force-fields to model interactions between atoms (or superatoms, if in the CG level).

For deriving potentials in the coarse grained level, there are many different methods (such as force-matching [1], iterative boltzmann inversion [2], relative entropy minimization, etc). Each of them allow being able to reproduce, by default (and in one extent or another), a given aspect of the system, related ofc to the specifics of the given potential-fitting strategy. It’s a good idea to get to know each method before making a decision on which one to use.

Now, in terms of softwares that have implemented these potential fitting methods, there are different ones. Depending on whether or not the method requires some MD calculations to be run, some of them allow using it conjugated with LAMMPS. You may checkout VOTCA. There is also one called IBISCO I think, but I am not familiar with. Most recently I also heard about this new one: OpenMSCG: A Software Tool for Bottom-up Coarse-graining | Theoretical and Computational Chemistry | ChemRxiv | Cambridge Open Engage, but I never used either.

I know also that MARTINI 3 [3] has force-fields for ionic interactions that were derived in the context of ionic liquids, so it could be that they are useful for you, especially if you are interested in reproducing thermodynamics of your system.

[1] Deriving effective mesoscale potentials from atomistic simulations - PubMed
[2] https://pubs.acs.org/doi/10.1021/jp044629q
[3] Martini 3: a general purpose force field for coarse-grained molecular dynamics | Nature Methods

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4

The short answer is Google. :slight_smile:

The longer answer is Google Scholar. :slight_smile:

You can look at the work of Urbakh and Bresme, who have recently parametrised some coarse-grained force fields for imidazolium ionic liquids.

But you should also take a step back and make sure you understand what you’re trying to simulate and what you need from your force field. Why coarse-grained instead of all atom (or polarizable, or even further down to DFTB or quantum methods)?

There’s nothing wrong with asking for help, but when you ask for help while providing very little information about what you’re doing and what you’ve tried, we run the risk of giving you lots of information that doesn’t apply to your situation and then wasting your time (as well as ours). :slight_smile:

1 Like
5

Thank you for your guidance.

6

Thank you for your inputs