8.4 Mopac calculation
This dialog window allows to run the Mopac
semi-empirical calculation. Press the Run button to start the calculation,
otherwise press Cancel to close the dialog. Please note that the Mopac
executables are included in the standard VEGA ZZ package. If you want use another
Mopac version, you must
replace the included executable placed in the VEGA ZZ installation folder with the new one.
When you press Start, a file requester is shown in order to select the output
file. Mopac runs in background and VEGA ZZ remains fully functional. When the calculation
ends without errors, the processed structure is automatically reloaded. To abort a
Mopac calculation, use the Task Manager or click with
the right mouse button on the 3D view and select Stop calculation.
Checking Update the 3D view, available only if Mopac2007/2009 is installed, the
molecule structure is automatically updated during the calculation and the
progress is shown in the console (step number, energy and gradient).
Checking Normalize the coordinates, the molecule is translated at the
Cartesian axis origin when the calculation is finished.
8.4.1 Parameter fields
With these fields you can specify the type of
calculation (AM1, MINDO/3, MNDO, PM3; MNDOD, PM6, RM1 if Mopac2007 is installed
and MOZYME, MOZYME RAPID, if Mopac2009 is isntalled), the total charge (if the pre-calculated charge is
wrong) and the extra keywords (Other field). The default parameter is AM1 and
the total charge that is calculated using the atomic partial charges if they are
already assigned, otherwise is calculated on the basis of the charge group
recognition. Is it possible that the molecule has wrong or incomplete atomic
charges and so a wrong value is shown. To force the group-based total charge
calculation, the user can click the Calc. button. To revert to the
default parameters, click the Default button.
When Mopac2007/2009 is installed, it's automatically recognized and the
graphic interface adapts itself to the new features (e.g. PM6, RM1 etc). Mopac2007 isn't included in the VEGA ZZ package and it can be installed following
these steps.
8.4.2 Switches
They are the main switches for Mopac calculation. To understand what they mean, please read the Mopac Manual.
Switch | Description |
Precise | Increase the criteria for terminating all optimizations by a factor, normally 100. |
GEO-OK | Override some safety checks (e.g. in the structure geometry). |
MMOK | Use the molecular mechanics correction for the amidic bonds (CONH). It can be automatically switched on if an amidic bond is detected. |
1SCF | Do a single point energy calculation. |
8.4.3 Limits
VEGA ZZ includes two versions of Mopac 7.01-4: Mopac_50_100.exe (max 50 heavy atoms and max 100 hydrogens) and Mopac_100_200.exe (max 100 heavy atoms and max 200 hydrogens). The two executables are selected automatically by VEGA ZZ for a balanced use of the hardware resources. No more than 300 atoms (100 heavy atoms + 200 hydrogens) can be used by VEGA ZZ in Mopac calculations. These limits can be superseded installing Mopac2007 (for more information, click here).