Potential

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1

Dear users

This is a general question in my mind and I will be tankful if one could help me:

Generally, if we want to simulate a system consisting of several atom types, how can we find that what is the correct potential model and coefficients of the model for those atoms?
For example in simulating a system consisting Na, Cl and C. We have eim files for Na-Na, Na-Cl and CL-Cl, and also airebo file for C-C modeling. But how can we model C-Na or C-Cl interactions?

Bests,

2

In this case, first principle md is a solution.

Best,

Yi

3

Dear users

This is a general question in my mind and I will be tankful if one could help me:

Generally, if we want to simulate a system consisting of several atom types, how can we find that what is the correct potential model and coefficients of the model for those atoms?

That question is as old as the method of molecular dynamics itself. I suggest you dig through some text book and original literature (and particularly review articles) discussing the derivation and parameterization of potential models.

For example in simulating a system consisting Na, Cl and C. We have eim files for Na-Na, Na-Cl and CL-Cl, and also airebo file for C-C modeling. But how can we model C-Na or C-Cl interactions?

It is not as simple as you make it. Potentials and parameter sets are derived for specific environments and to reproduce certain properties (more or less well). You cannot easily mix and match those without careful consideration. Even if it would be technically possible, you might an imbalance which can lead to significant systematic errors up to computing complete nonsense.

Axel

4

In this case, first principle md is a solution.

Or not. As it may be prohibitively expensive and will only allow for very short trajectories.

5

Or developing a specific force field from first principles. Your problem isn’t only the C-Na interactions and C-Cl interactions:

C-Cl-Na?

C-C-Cl

C=C-Cl

C-=C-Cl

And so on. Basically just because you have a field for Na-Na interactions, that doesn’t mean it’s valid when carbon is present, nor is AIREBA valid when Na or Cl are present. These force fields might be helpful as starting points, but they are perturbed by the presents of other elements.