How to fast optimize large molecule?

07 July 2018 0 10K Report

Dear Friends and colleges

I have a problem in optimization of geometry of molecule, which contains large number of atoms. I used B3LYP/6-31g (d, p) to optimized structure of molecule. Unfortunately, I found “convergence failure” at the end of log file. I added SCF=QC on the line of input file. The calculation still on the road. I saw people try to use semi-empirical key word such a PM3. I try to use PM6, but still I get “convergence failure”. Please guide me. What can I do?

Please find input file in the attachment.

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