Potential Definition Discrepancy with Stress Calculation

[camdennis]

I was hoping I could get someone else to check that I'm not just being dense, but after noticing that the stress response was opposite in sign to what I expected, I noticed that quantity.stress seems to be different than the virial definition of stress given by (for example) https://en.wikipedia.org/wiki/Virial_stress

I think it's just an overall negative sign. In athermal systems, I thought dU/dV was the definition of the stress tensor. As always, I'm happy to be wrong, but would be extremely appreciative if someone smarter than me could take a look. Thanks!