Is it possible to build a custom force field

Dear All,

I am trying to simulate a coarse-grained polymer melt, more specifically PDMS at NPT conditions. Since it isn’t a very well studied system, I am referring to coarse-grained parameters obtained by Huang et. al (2017) [1] using the TEAM-MS force field.

I have check the various pair, bond, angle and dihedral styles in LAMMPS and it doesn’t provide the full description in line with my Model. Notably, this force field has a pairwise epsilon parameter that is time dependent. It also has a bond-angle interaction term that is slightly different from the class2 force field, having just one term.

So is there a way in LAMMPS I can customize the available styles to obtain the force field desired to be evaluated?

If not, due to LAMMPS being an open-source distribution, is it possible to add this desired force field styles? And how do I go about doing this?

[1]: Hao Huang, Fenglei Cao, Liang Wu & Huai Sun (2017) All-atom and coarse-grained force fields for polydimethylsiloxane, Molecular Simulation, 43:18, 1513-1522, DOI:10.1080/08927022.2017.1328597

Thanking You,
Kavipurapu J Pundarikaksha
B.Sc (Research) Physics

Senior Year
Shiv Nadar University

NH-91, Dadri, Gautam Buddha Nagar
Uttar Pradesh 201314, INDIA.

i cannot comment on the time-dependent epsilon, since it is not clear how that would work and i don’t have the time to read up on it.

as for using only selected components of a potential function. that is easy: you can just set the force constants of the undesired components to zero.

as for customizing LAMMPS: there is a whole section about this in the manual.
https://lammps.sandia.gov/doc/Modify.html

axel.