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Re: Long time optimization

Amir Nasser Shamkhali

Dear Khimich
Your input structure is too far from an actual structure. For instance, the C-C bond length is 2.65 angstrom in the ring. Such a big bond distance is not near an actual bond length in organic compounds. Therefore, before calculation, you may need to use one or both of these corrections:
1) Try to make your input structure with an appropriate molecular editor software in order to cunstract more realistic structures (see the "Related" page of this site).
2) For organic compounds, a previous optimization with semiemprical methods such as AM1, PM3, MNDO, and etc. is usually fast. Then use the output of this optimization as input structure for final optimization.

Best Wishes

On Fri Feb 25 '11 3:35pm, Khimich wrote
>Sometimes the optimization requires a lot of iterations. For example, if there is SO2R - group, for some dihedral angles rotate very slowly. Is there any way to speed up the calculation?

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