Follow this discussion.

https://www.researchgate.net/post/How_can_I_resolve_the_convergence_failure_error_in_Gaussian_09

I think this will be helpful for you.

Thanks.

Thanks Abdul,

I read the discussion suggested by you and also tried to follow some suggestions given in that discussion. But when I tried with scf=(maxcycle=3000) scf=xqc, I am getting an error termination. I am here by attaching a screenshot of the error. Please have a look an suggest me some way out. It would be very helpful for me.

Thanks.

Hi Megha,

when you have to deal with anions usually diffuse basis functions are necessary, because the additional electron might not be in the valence region. Did you take that into account?

Hello Arnim,

I am working on gold clusters. For a gold cluster I want to see the O2 adsorption. I optimized the neutral structure by using SDD basis for gold and TZVP basis for oxygen. Now I want to deal with charged cluster. The SCF convergence problem is coming in some of the isomers and not in all. I tried with SCF=(maxcycle=3000) scf=xqc. But then job is terminated with an error. Is that not sufficient while dealing with anions?

Hard to say what the reason might. Maybe try a better basis set.

Also, you could check the spin state. Maybe with a pseudo-Fermi smearing for the occupation numbers, if that is available in the program you are using.

Or you ran into a multireference problem.

Thank you Arnim.

I shall try with different spin state. But if anyobdy have other solution please give suggestions.

Thanks.

Hello!

Does anybody know how to use scaled steepest descent method instead of Newton - Raphson in Gaussian - package?