NPT-MD simulation under the periodic boundary conditions

[Yuta-Yoshimoto]

Dear Allegro developers,

We have tried running NPT-MD simulations of organic molecules under the periodic boundary conditions.
We trained our Allegro model on the ANI-2x dataset, which includes quantum chemical calculation data of small organic molecules composed of H, C, N, O, F, Cl, and S atoms in a vacuum state (i.e., non-periodic boundary).
During the training, we included the StressForceOutput option and trained the model using only force values.
Then, the force MAE on the test set was about 0.73 kcal/mol/angstrom, which seems to be sufficiently small.

Using the pair_allegro package and the potential file extracted from the trained model, we performed NPT-MD simulations of 100 2-chloroethanol molecules (300 K, 1 atm) using pair_style allego3232 in LAMMPS.
Then, we found that the system density continued to decrease, exhibiting a very low value below 0.1 g/cm^3.

I am wondering whether the Allegro model with the StressForceOutput option trained on the forces of isolated molecules under the non-periodic boundary conditions can be applied to NPT-MD simulations of condensed systems under the periodic boundary conditions.

We used the following packages:
NequIP: main branch (latest, v0.5.6)
Allegro: main branch (latest)
pair_allegro: multicut branch

I would really appreciate it if you could give us some comments on this issue.

Best,
Yuta

[Linux-cpp-lisp]

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