Inconsistent runtime error when using a nequip model to preform Langevin Dynamics in ASE🐛 [BUG]

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Inconsistent runtime error when using a nequip model to preform Langevin Dynamics in ASE🐛 [BUG]

[Linux-cpp-lisp]

Hi @NicholasHattrup ,

ValueError: After eliminating self edges, no edges remain in this system.

This error means that for the given system state and cutoff, every single atom has no neighbors. The vast majority of the time this is a sign that something is wrong (such as trying to set the cutoff in the wrong distance units), and so we made it an error. In MD, it could also be a sign that your simulation is exploding.

What kind of system are you simulating, and have you checked the trajectories that throw this error? Do they look physically plausible / is having a system state with such low density reasonable for your application? If it is, I can make this a configurable option to suppress the error. Note that in the case where all atoms have no neighbors, the predicted forces on all atoms will be zero, since the total energy will consist only of constant per-atom and global shifts (depending on your configuration).

[mhellstr]

I ran into the same ValueError and noticed that it disappeared when I increased r_max. It would be great if the message was more helpful (f"Every single atom has no neighbors within the cutoff r_min: {r_min}")

[Linux-cpp-lisp]

Hi @mhellstr ,

Good point--- changed on develop: da3e4bd

[mhellstr]

Thanks, although now that I think more about it I don't think this should really be an error. It would be great to use nequip to train/predict the H2 or O2 energy as a function of distance, for example (dissociation curve). Then it would be awkward to only be able to predict points inside r_max.

[Linux-cpp-lisp]

Quoting the above,

The vast majority of the time this is a sign that something is wrong (such as trying to set the cutoff in the wrong distance units), and so we made it an error. In MD, it could also be a sign that your simulation is exploding.

But like I said if people need it I'm happy to make an option to suppress this error.