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Panwang Zhou
pwzhou@gmail.com

Thanks for you comments.

So my system should not have the PJT effect and I will try to improve both the active space and basis set to obtain the optimized geometry with C2v symmetry. Thanks.

Best Regards,

Panwang Zhou

On Wed Dec 6 '17 10:10pm, Alex Granovsky wrote
----------------------------------------------
>Dear Panwang Zhou,
>Dear Pedro,

>this is most likely the manifestation of a problem known as
>the "Pseudo Jahn-Telller effect". See papers and reviews by
>I. B. Bersuker on this:

>https://scholar.google.com/citations?user=maHGAPQAAAAJ&hl=en&oi=sra

>In most cases these effects are caused by incompleteness of
>active space or poor orbital basis, or both.

>Hope this helps.

>Kind regards,
>Alex Granovsky
>
>
>
>
>
>On Wed Dec 6 '17 4:15pm, Panwang Zhou wrote
>-------------------------------------------
>>Dear Pedro Silva,

>>I have tried to request the C2v symmetry in DATA deck and set NOSYM=0 in the control section, however, it seems that this did not take effect, because from the second step, the geometry has changed the symmetry.

>>On Mon Dec 4 '17 4:47pm, Pedro Silva wrote
>>------------------------------------------
>>>>Dear Panwang Zhou,

>>>Your output states that you did not request C2v symmetry in the optimization algorithm. In your DATA deck, you should replace the C1 line by "Cnv  2" , followed by a blank line and by your geometry, suitably rotated/translated/etc to comply with the internal master frame detection conventions:

>>>By default, the 'master frame' assumes that
>>>1. z is the principal rotation axis (if any),
>>>2. x is a perpendicular two-fold axis (if any),
>>>3. xz is the sigma-v plane (if any), and
>>>4. xy is the sigma-h plane (if any).
>>>Use the lowest number rule that applies to your molecule.
>>>
>>>
>>>Some programs (eg. ChemCraft) allow you to select the symmetry and automatically generated properly-formatted $DATA groups to ensure that your computation does not face trouble because of deficient adherence to those conventions.

>>>