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Pedro Silva
pedros@ufp.edu.pt

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.