...
Sulfonamide issue with 1.3.0, rectified in 1.3.1
...
Parsley parameters - From Hyesu’s summary (linked above)
Parameters a30, a31 are found to be going in the direction of nonphysical values over generations of force fields.
Parsley parameters - From Hyesu’s summary (linked above)
| SMIRNOFF99Frosst | Parsley 1.2 | Parsley 1.3 |
|---|---|---|---|
a30 | 109.5 / 140.0 | 104.2 / 201.1 | 99.1 / 220.7 |
a31 | 109.5 / 120.0 | 96.3 / 152.3 | 89.8 / 188.4 |
*equilibrium angle (degree) / force constant (kcal/mol)
The “The equilibrium angles of a30 and a31 decreased while their force constants increased. And during the refitting of Parsley 1.2, the values moved further away from the very initial points (in SMIRNOFF99Frosst)
During the course of MD in a bound structure, NH2 of the sulfonamide is being pulled in close to the SO2 oxygens. The O-S-N angles go down to around 72 degrees and the distance between oxygen and hydrogen goes down to around 1.7 angstroms. Test simulation with a simple sulfonamide in water showed the same pathology, while it did not happen when using SMIRNOFF99Frosst.” - Hyesu
Investigating the training set and test set sulfonamide optimized geometries didn’t reveal any pathology and they seem to agree well within accepted thresholds. This is significant since we cannot capture these silent errors unless we run MD.
Also, in-ring geometries don’t have an effect even though they’re part of optgeo targets that target these parameters.
...