Verify whether the potentials are correctly applied

LAMMPS LAMMPS Beginners
1

Is there any method to verify whether the potentials, particularly when multiple potentials are used in the same script, are correctly assigned to the intended atoms? I am dealing with multiple systems that share some common elements, and I want to confirm that the potentials are accurately applied before proceeding with the simulation.

2

You have two problems here:

  1. is your setup conceptually correct?
  2. have you implemented it correctly?

As a beginner in LAMMPS the chance is very high that your input is already failing at point 1. And then worrying about point 2. is a waste of time.

This statement is particularly worrying. In classical MD you don’t look at “elements” but “atom types” and there you can have multiple different “atom types” for the same elements when their “chemical environment” or behavior is different. Sometimes people use different atom types even for equivalent atoms to simplify analysis later.

Combining different force field types in the same calculation is almost always a mistake, since the respective parameterization was done under different strategies (e.g. difference balances between coulomb and dispersion and different methods to map the charge distribution from a quantum calculation to point charges). Mixing many-body and molecular force fields is even more problematic.
Throw in a dash of ReaxFF and trouble is almost guaranteed.

Bottom line, as a beginner it is a bad idea to even start such a project. You first need to build your skills where you can tell the difference between success and failure and then gradually over time gain experience with more complex setups.

Update:

That said, the way to verify that your input works as expected is independent from the complexity of the force field. You define all atom types, bond types, etc. but then construct a data file where only a subset is used where you can compute the forces and energies manually and compare. You can turn off styles by using “none” or you can use style “zero” and this way check individual pairs or triples of atoms and so on.

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