periodicity with NEIGH-RVEC-F


I have written out a MEAM model that is very different than the 2NN MEAM model, and I’m currently debugging it.

I apologize if my preceding issue and question may be fundamental, but I’m hoping that maybe someone can help me:

In my KIM model, the requirement is for periodic boundary conditions to exist. From what I have read in the OpenKIM googlegroup, MI-OPBC has not been implemented in LAMMPS yet (I’m using the KIM API with LAMMPS, BTW). Slide 27 of the workshop presentation ( mentioned that general periodic boundary conditions can be implemented with NEIGH-RVEC-F NBC method. However, in my model, I am unable to call the boxSideLengths of the box, which compose the boundaries, despite trying to unpack them from kim_api_getm_data subroutine.

How does one get the box lengths through the KIM API for a model? Am I using the wrong subroutine? Or is extraction of the boxSideLengths reserved only for a model driver?

I would very much appreciate help in this.


There is no boxSideLengths defined for NEIGH-RVEC-F/H. Periodic boundary conditions can be created using the NEIGH-RVEC scheme, but the Model has no way of knowing that this is what the boundary conditions are or what the box size/shape is.

If the model explicitly depends on the periodic box sizes in order to compute energy and forces etc., then it can't be implemented with anything other than the MI-OPBC scheme. However, I think such models are rather rare.