How can you manage SCF convergence problems? "Failure to locate stationary point, SCF has not coverged"


This is the most annoying message after Optimization run ( even with a good primary start geometry like UFF we ay see that) .
The only solution I know is to use the output log file for another run but it is very time consuming.
Is there any way to force GAMESS to automatically do that ?( I mean makes another automatic run on current output results ).
There can be many reasons for the SCF to not converge.


The initial guess wasn't great, and the convergence is slow. Increasing the number of SCF iterations can help here.
The SCF oscillates. This can happen if there are two orbitals close in energy. Using damping, mixing (i.e., the next iteration is 50% the old and 50% the updated iteration), Fermi broadening, etc. can help here.
The SCF strategy (e.g., DIIS) is causing problems. Usually DIIS can greatly accelerate convergence, but in some hard-to-converge systems, you need a lot of iterations with another strategy (e.g., Newton-Raphson)


Without more information from your particular file, it's impossible to know how to help. Many times, you may simply want to increase the maximum number of SCF iterations and it'll work fine.