2021-01-19 Meeting notes

Date

Jan 19, 2021

Participants

  • @Simon Boothroyd

  • @Michael Shirts

  • @Owen Madin

  • @David Mobley

  • Shuai Liu (XtalPi)

  • Mingjun (XtalPi)

Goals

Discuss the current status of the BCC refitting collaboration and determined next steps.

Discussion topics

Time

Item

Presenter

Notes

Time

Item

Presenter

Notes

Current status

https://openforcefield.atlassian.net/wiki/spaces/FF/pages/1128071183

@Simon Boothroyd

Proposed next steps

Several possible directions:

  • Start optimisation / solve least squares problem direct. Are we stuck in a local minima?

    Don't necessarily need to benchmark produced charges, but would be good to see how different they are.

  • Ethers seem to be the most problematic. Need to analyse this further.

    • Perform analysis of the gradients during fitting - are ethers trying to constrain the parameters differently than the rest of the data?

    • Split the analysis into polar and non-polar. Electric field expected to yield better results for polar molecules over non-polar. Need to determine if the test set is balanced too much towards non-polar.

    • Potentially look more into fitting to ESP rather than electric field?

  • Maybe we need to expand the sets to include some nitrogen data to see the real benefits of the refits?

@Simon Boothroyd

  • OM - Adding N data would be large expansion of the scope. Need to rethink data set, number of BCCs involving N very large. Benefit of looking at smaller set is allows to tease out more easily the subtle effects going on.

Action items

@Owen Madin: Restart the BCC optimisations from randomly perturbed AM1BCC parameters.
Analyse whether the alcohol issue was resolved by the BCC optimisation.
Optimising the BCCs against phys-prop data (both with and without QM regularisation)
Analysis of ethers performance (especially looking at gradients).
Comparing the charges produced by the BCC study with the GAFF study.

Decisions