The Minimize option performs a full quantum-mechanical geometry optimization using Psi4. It optimizes bond lengths, bond angles, and torsion angles using DFT.

To optimize a molecule:

1. Read a chemical structure into ICM.
2. Convert the chemical to a 3D ICM object.
3. Check that the atomic formal charges are correct, as these determine the total molecular charge.
4. Select MolMechanics/Quantum Mechanics/Minimize.

The default calculation method is B3LYP/6-31G*. During optimization, molecular energies and gradients are calculated and the geometry is adjusted to minimize the energy.

Optimization finishes when the convergence criteria for energy, forces, and displacement are satisfied, or when the maximum number of optimization steps is reached. The default maximum is 50 steps.

Energy units: Psi4 calculates energies in Hartree units. ICM converts these values to kcal/mol and reports them in the terminal window.

Command-line reference: minimize quantum.