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)
Input force field : version 1.1.0 parsley (http://doi.org/10.5281/zenodo.3695094)
The objective function decreased from
8.710e+03to6.843e+03in 31 steps.
Initial X2 | Final X2 | |
|---|---|---|
v1.2.0-RC1(https://openforcefield.atlassian.net/wiki/x/AQC4F ) | 3.619E+04 | 6.877E+03 |
v1.2.0-RC2 | 8.710E+03 | 6.843E+03 |
Benchmark Results
Benchmark data
For the calculation, full benchmark set was used (25168 optimized geometries, plus relative energies of 2005 molecules). Detailed of the molecule selection can be found here: release-1-benchmarking/QM_molecule_selection
(1) Comparison of objective values from single point calculations on benchmark full set
Two types of benchmarks were done to compare the performances: (1) QM vs MM optimized geometries and (2) the relative energies between conformers at “QM optimized geometries”. The final objective function value(X2) from FB single point calculation gives a brief overview of the agreement between QM and MM. The lower X2 is, the better the force field reproduces QM structures and energetics.
| objective value (X2) |
|---|---|
initial guess | 29,469 |
v1.1.0 | 20,097 |
v1.2.0-preliminary (link: http://doi.org/10.5281/zenodo.3781313 ) | 16,939 |
v1.2.0-RC1 | 16,713 |
v1.2.0-RC2 | 16,910 |
(2) v1.2.0-RC1 vs. v1.2.0-RC2: Parameter comparison
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)
: bond/ angle coverage check? -> origin of large k value for a15 (Wed or later today)
: QM vs. MM scatter plot comparison? (Wed or later today)
Torsion terms with significant different final k values between RC1 and RC2:
t146,t147: 6 periodicitiest15([*:1]-[#6X4;r3:2]-@[#6X4;r3:3]-[*:4]),t16([#6X4;r3:1]-[#6X4;r3:2]-[#6X4;r3:3]-[*:4]): in-ring rotation
