JH – For some reason this won’t converge. MAybe big problems with sterics? Or priors are too large?
DM – Tobias had done work on inferring torsions from scratch. You may benefit from interfacing with that.
JH – That could be useful
DM – Tobias should be in a similar time zone to you. We’re not trying that yet for FF fitting.
…
DM – It wouldn’t surprise me if the periodicity and phase needed to be different now
JH – We could try that with bespokefit?
DC – What happened during training? Were torsion scans used or single points?
JH – Same training method as befspokefit uses.
DC – So there’s no DEXP torsion scan in the training.
JH – …
PB (chat) – Does Sage also show this kind of off-minima profile for this molecule?
JH – Yeah, Sage looks pretty bad here too.
CC – 1-4 scaling?
JH – Yup, that’s used. We optimized the scaling factor and didn’t see much improvement, so I don’t think that’s the problem
DC – Could be good to start with simpler molecules
JH – Agree
DC – I don’t understand why it doesn’t converge if it’s not getting better.
JH – Saw the same with the espaloma FF (?)
DC – But those were distorted structures, I don’t know why this would have the same.
JH – Are ring torsions optimized every time?
DM – We optimize the ones that are covered by the dataset, which may include ring- and non-ring torsions.
PB – I think sage doesn’t have too many in-ring torsions, and even if it has it they have separate parameters. An additional analysis for the DEXP paper could be dimer interaction energies. So Sage vs. DEXP could be handy
JH – Not sure how useful those would be if we’re aiming to model condensed phase, since dimer energies are vacuum.
DC – Bill Jorgensen starts his fits using dimer energies, but I don’t like that method. I think it’s useful to get the right order of magnitude, but in terms fo small charges to potential energy surface it’s not going to help much.
PB – Should I do another valence parameter fit with relaxed priors?
DC – You could do that. I’d suggest waiting until JH has done a wider analysis of current issues. I’d love to avoid redoing the transfer free energies. .
DM – I’d want to make sure that we have good evidence that doing something differently will make it better.
