Stress support

[davkovacs]

We have several projects that would greatly benefit from openmm-torch supporting ML models returning stress (not only energy and forces). This way we could use OpenMM for running NPT simulations using ML force fields.

[raimis]

You can already use TorchForce for the NPT simulations. The barostats in OpenMM don't need stresses.

[davkovacs]

Sorry, I did not realise OpenMM uses a Monte Carlo barostat. In that case there is no problem. We will give it a go.