2024-07-10 FF Fitting Meeting

Participants

  1. @Brent Westbrook

  2. @Trevor Gokey

  3. @Chapin Cavender

  4. @David Mobley

  5. @Alexandra McIsaac

  6. @Lily Wang

  7. @Michael Gilson

  8. @Pavan Behara

  9. @Jeffrey Wagner

Discussion topics

Item

Presenter

Notes

Item

Presenter

Notes

Hessian/frequency fitting

 

TG

  • TG will upload slides here

  • Recording: https://us06web.zoom.us/rec/share/m8K3N8iPp4UGsmcvLTS6E89c0uCBIhQomQvxn6A9ojS9CFuWODdNF3N1RyxZ-y27.PrnWASqZUg8SnsTq
    Passcode: 0wVgTc*m

  • PB – Re: scaling of angle force constants - Could you repeat?

    • TG – I fit the angle’s k values and scale the force constant by about 1.5. This was because I observed the vibrational modes from 1000 to 1500 cm-1 being underestimated (sub 1k is generally torsions, but 1k-1.5k is angles).

  • DM – If I were skeptical and said “these FFs are no better than the starting FF”, what’s your best counterargument?

    • TG – I don’t have a starting point, so the fact that this gets close to our multi-generational FFs is impressive. This also allows us to iterate on different approaches to chemical perception.

    • PB – So this’d be fairer to compare to MSM values?

    • TG – It’s closer, but MSMs are trained on Sage torsion profiles.

    • DM – So the roche set one - how much chemistry does that cover? Is that potentially a general FF/could that be fit as a general FF and tested?

    • TG – I’m not super familiar with the composition of the Roche set. I might include a larger set/take the sage optimization sets to use as input.

    • DM – It’d be cool to compare a full run of this to a “real” FF

    • LW – Yeah, if you could output this as an OFFXML we could plug it into the other fitting machinery.

    • TG – That’d be cool.

    • LW – Any thoughts on why torsions are underesimtated?

    • TG – I’d love to talk to Cole group about this.

    • BW – I’d tried using the algorithm from the paper, ended up with really high force constants, I thinkn there was some interaction between nonbonded.

    • TG – Might that be because you were forcing the sage periodicities? My BAT result showed some things exploding for certain perioditicites. But this was better with lower ones. I need to move on to other work soon but I could include some new datasets if folks send me the dataset IDs.

    • LW – How long does it take?

    • TG – MM hessians take about 1 min per molecule, so the current fits took me about 30-60 mins.

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Short update to condensed phase fit

LW

  • LW will link slides here

  • JW + PB – Exactly 0.1 kcal/mol? And which version?

    • LW – 0.418 kJ/mol is what I saw, using old evaluator.

  • DM – Did this affect vsite stuff?

    • LW – Unlikely by my judgement

  • JW – Seems like there are two major courses of action

    • Commit to finding the root cause

    • Add this to the “if a FF fit smells funny” checklist

  • JW – I suggest course 2, though I’ll keep looking for possible root causes.

  • DM – Agree.

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Action items

Decisions