16.10 Handling difficult cases: When SCF does not converge

General suggestions:

Before you start you should check:

If convergence problems persist, the following techniques can be attempted:

Hartree-Fock options & Small-basis initial guess:

Cationic or Anionic initial guess:

Density-functional initial guess:

If all else fails: Use the MCSCF program. The MCSCF program uses an advanced orbital optimization algorithm which is much more robust than the SCF method, and which can converge almost everything you give to it (but it is often slower and sometimes locks on an excited state if started from an atomic density guess). MCSCF can also calculate Hartree-Fock solutions if used with suitable input cards.

molpro@molpro.net 2020-04-18