Setting Parameters in LAMMPS using kim_param

OpenKIM
1

Hello,

I’m trying to use Lammps-29Oct2020 version to utilize OpenKIM in some metal simulations. I’m using the Portable Model " LJ_ElliottAkerson_2015_Universal__MO_959249795837_003". The PM parameter set provided (https://openkim.org/files/MO_959249795837_003/LennardJones612_UniversalShifted.params) led me thinking the parameters were defined as “sigma” “epsilon” and “cutoff”.

The problem I have is in setting new parameters through lammps input file. When I use the command:
kim_param set sigma 3 3.73

I get the error:
This Model does not have the requested ‘sigma’ parameter (…/pair_kim.cpp:463)

Am I missing a Readme file that provides a list of the parameter names?

PS: Just started trying OpenKIM, after years of ignorance. It is wonderful.

2

Hello,
Thanks for your kind words about OpenKIM! It’s great to hear that users are finding it helpful.

If you look at the lammps log output from the kim init ... command, you’ll see something like

#=== BEGIN kim init ==========================================
units real
neighbor 2.0 bin   # Angstroms
timestep 1.0       # femtoseconds

This model has 4 mutable parameters.
 No.      | Parameter name     | data type  | extent
-----------------------------------------------------
 1        | shift              | "Integer"  | 1
 2        | cutoffs            | "Double"   | 9730
 3        | epsilons           | "Double"   | 9730
 4        | sigmas             | "Double"   | 9730
#=== END kim init ============================================

So, the param_name you need to use is sigmas (it is plural, not the singular sigma you used).

Hopefully, that clears things up and will let you achieve your goal.

Cheers,
Ryan

3

Hi Ryan,

My bad, I was initializing kim and then switching to another log file for the simulation. So those valuable lines remained on the default log.lammps file I never check.

Thank you a lot for the information.

Marcel