I am using Forcite (Geometry optimization) to minimize an organic molecular structure (CCDC reference name: PUVRIH).
However, after the optimization, total energy comes out to be a ‘positive’ term instead of commonly observed negative values. It seems I am doing something wrong here. Can anyone please guide me ?
Parameters used for minimization are as follows:
Force field: Dreiding
Charges: QEq
Quality: Ultrafine
Electrostatic: Ewald
van der Waals: Atom based
Algorithm: Smart
Max iterations: 1000000
Optimize cell has been checked too.
Results observed:
---- Initial structure ----
Total enthalpy : 359.295788 kcal/mol
External pressure term : 0.000000 kcal/mol
Total energy : 359.295788 kcal/mol
Contributions to total energy (kcal/mol):
Valence energy (diag. terms) : 249.591
Bond : 203.474
Angle : 40.674
Torsion : 4.859
Inversion : 0.583
Non-bond energy : 109.705
Hydrogen bond : 0.000
van der Waals : 100.922
Long range correction : -0.861
Electrostatic : 9.644
rms force : 5.523E+001 kcal/mol/A
max force : 1.208E+002 kcal/mol/A
rms stress : 2.027E+000 GPa
max stress : 3.468E+000 GPa
Cell parameters: a: 8.759000 A b: 10.554000 A c: 10.606400 A
alpha: 114.116 deg beta: 96.957 deg gamma: 97.535 deg
---- Final structure ----
Total enthalpy : 131.924374 kcal/mol
External pressure term : 0.000000 kcal/mol
Total energy : 131.924374 kcal/mol
Contributions to total energy (kcal/mol):
Valence energy (diag. terms) : 75.409
Bond : 28.981
Angle : 43.902
Torsion : 2.058
Inversion : 0.468
Non-bond energy : 56.515
Hydrogen bond : 0.000
van der Waals : 43.804
Long range correction : -0.815
Electrostatic : 13.527
rms force : 1.986E-004 kcal/mol/A
max force : 8.959E-004 kcal/mol/A
rms stress : 1.161E-005 GPa
max stress : 2.586E-005 GPa
Thanks,
Bhavin
