Hello,
I am having a problem with structure optimization.
My molecule contains a cyclopropane ring structure. (Also other types of rings too.)
When calculation ended, this ring is not maintained.
I really want this ring to remain.
How can I solve this problem?
Thank you:)
You could work with frozen internal coordinates, so work in the following three steps:
1) Optimize the cyclopropane ring (hydrogen saturated) with your desired functional and basis set.
2) Insert the optimized structure into your starting geometry. Freeze the internal coordinates of the cyclopropane ring during the following geometry optimization as described here:
http://gaussian.com/gic/
That should give you a structure in which your internal cyclopropane ring coordinates remain unharmed but the rest is optimized.
3) Remove all freezing commands and rerun the optimization (use the preoptimized orbitals from the previous step to start). That way you should end up with intact cyclopropane rings. If they still open, you should doubt their stability in real life.
Dear Lucy Ryou,
In addition to the advice given by the colleague Jürgen , i suggest you to see link and attached file on topic.
http://wild.life.nctu.edu.tw/~jsyu/compchem/g09/iops2.pdf
Best regards
Is there an article that suggests that this structure has already been optimized by quantum methods (used in another computational article) or even used in experimental work? If your answer is yes. So this structure is stable and should not be changed after optimization.
So, changing the structure for that is usually happened due to the improper initial structure. Also, you must check your basis set because this could be an effect of a basis set.
on combining the two molecules in gaussian 09, after optimization the molecules are separated.why
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