Thank you very much for your help.
Sincerely,
]]>If you are using G16, the "int=ultrafine" is default keyword, you do not need to manually specify it.
If you are using G09, the difference in the geometries optimized using "int=fine" and "int=ultrafine" is usually negligible and thus you do not need to repeat all calculations. However, if the studied system is weakly bounded complex or the structure is quite flexible, it is best to make all optimizations conducted at the same quality of integral grid.
Tian
]]>Note: I forget to use the keyword, and the optimization converged.
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