- Preconditioned Conjugate Gradient:

By adding the keyword PCG you enable the preconditioned conjugate gradient minimizer which improves in almost every aspect over steepest descend. Its convergence behavior can be tweaked with the TIMESTEP ELECTRONS keyword. The default time step value is chosen for CP-dynamics rather than wavefunction optimizations, so setting it to a value like of 10.0-20.0 usually speeds up convergence.