When I use Universal force field in geo opt for single molecular, I found that the energy of the final structure in the result was different from the single-point energy of the optimized structure. If I performed another opt opt for the optimized structure, the differenc bewteen the two energies would reduce. When I use COMPASS as the force field, there is no difference.
Force filed | 1st Single-point energy | 1st Geo opt | 2nd Single-point enrgy | 2nd Geo opt | 3rd Single-point enrgy | ||
Initial energy | Final energy | Initial energy | Final energy | ||||
COMPASS | 168.593035 | 168.593035 | 17.781290 | 17.781290 | 17.781290 | 17.781290 | 17.781290 |
Universal | 1701.033367 | 1701.033367 | 37.591299 | 43.662489 | 43.662489 | 41.058536 | 40.481757 |
I think the single-point energy of the optimized strcuture is reasonable, compared with the energy of the final structure in the result of opt. In the case of Universal force field, the charges are calculated once by the selected method (current chare, QEq or Gasteiger). However, the charges based on the initial structure are not correct for the optimized structure.
My question is: how to let the forcite module calculating charge after each opt cycle when selecting Universal force field?
