Page Comparison

Note: This post will be moved to Force Field / FF releases / Parsley minor release(s) once it is ready to be shared.

Fitting Data and Results

• Fitting targets: 2nd generation training sets (link for the details of the training set generation scheme: http://doi.org/10.5281/zenodo.3777278)

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• Direct parameter comparison has found no significant differences in equilibrium bond lengths and equilibrium angles while showing notable differences in k values of some angle/ torsion parameters.

• Angle terms with significant different final k values between RC1 and RC2:

  • a6([#1:1]-[*;r3:2]~;!@[*:3], k value in SMIRNOFF99Frosst: 100 kcal/mol/radian²)

  • a3([*;r3:1]1~;@[*;r3:2]~;@[*;r3:3]1, k value in SMIRNOFF99Frosst: 200 kcal/mol/radian²)

  • a15([#8X1:1]~[#6X3:2]~[#8:3], k value in SMIRNOFF99Frosst: 126 kcal/mol/radian²)

: Based solely on my intuition without no strong evidence, RC2 angle k values for the angle terms(doesn’t change much from 1.1.0 during the optimzation) seem physical; 400kcal/mol/radian² for angle seems too large compare to other angle k values. Final gradients for the angle k values are also higher in RC1 (a6: 5.580e+00 , a15 : 4.750e+00) compared to the gradients in RC2 (a6: 1.599e+00 , a15 : 1.391e+00)

*need explanation on the following figures

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This is Here's one example of good examples of having equilibrium angle which is far from angles in QM optimized geometries. Having larger equilibrium angle for a38 helps in locating hydroxyl hydrogen in phosphono group far away enough from its neighboring oxygens, preventing unphysical intermolecular H-bonding.

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• Torsion terms with significant different final k values between RC1 and RC2:

  • t146, t147: 6 periodicities

  • t15 ([*:1]-[#6X4;r3:2]-@[#6X4;r3:3]-[*:4]), t16 ([#6X4;r3:1]-[#6X4;r3:2]-[#6X4;r3:3]-[*:4]): in-ring rotation

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Specific improvement in certain functional groups(phosphono group, sulfamate acetate) found in RC1 is also shown in RC2.

• TODO: revert WRMSE → objective value

• TODO: implementation of RMSE calculation from FB output

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QM optimized geometry of CC(O)([P@@](=O)(O)[O-])[P@](=O)(O)[O-]. ( orange: MM optimized geometry with v1.1.0 force field, green: v1.2.0-RC1 force field, magenta: v1.2.0-RC2 force field)

(4) v1.2.0-RC1 vs. v1.2.0-RC2: Relative energies between conformers at “QM optimized geometries”

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