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Roman Zubatyuk
zubatyuk@gmail.com

Yes, imaginary frequencies mean that you got saddle point. Although, low value of first frequency means that you have a maximum with a flat slope. Unfortunately, you did not put the input file in attachment, so it is difficult to say if there any problems with it. But the general solution is:
1. use final geometry
2. use hess=read in $statpt and put calculated hessian in the input file
3. use stpt=.t. and ststep=0.1 (most effective value could vary) in $statpt
4. run optimization
This will instruct program to jump away from the maximum.

Good luck!
Roman Zubatyuk.

On Thu Jan 7 '10 0:31am, Alexandr wrote
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>Hi,
>A hapy new year to all clubmen of fans and users of program FireFly! (By the way, I am very glad that my offer on FORUM from Mon Nov 16'09 to name FireFly through two capital letters have been met by administration FORUM favourably; or in abbreviated form "FF". It already has had time to make Marec Pawel Checinski in last version of the management - look section Tutorial of present FORUM).
>     I count hessian and frequencieses for a series from nearby 20 similar organic molecules consisting of 40-48 atoms of carbon, hydrogen and nitrogen. The geometry of molecules has been preliminary optimised in the same basis with average indexes: GMAX 0.00007, GRMS 0.00003; opttol=1e-9. Attempt to use opt

>     1. A standard situation. All calculated frequencies are positive and there is no abusive message THIS IS NOT A STATIONARY POINT ON THE MOLECULAR PES. THE VIBRATIONAL ANALISIS IS NOT VALID!!! In many articles it is informed on this situation as about the proof of correctness of the performed work of optimisation - (local) minimum on PES has been reached.
>     2. A Non-standard situation. All calculated frequencies in IR spectrum REAL, but FF are printed by the abusive message specified above. What to do in this case, I already asked council at FORUM (Mon Nov 16'09). I have received the answer from all of us respected Alex Granovsky. Certainly, its answer was fine and settling, but, unfortunately, calculated on the prepared listener. Therefore I have understood only that in this case the abusive message can be ignored.
>     Unfortunately, logically arguing, there can be one more variant of a non-standard situation. And it (O, mein Gott!) it was showed at calculation of 16th molecule under the account! The abusive message is not present, but the first calculated frequency in IR spectrum IMEGIN. That is it can be saddle a point. But similar I do not expect anything. What horror, after all to improve optimisation by w>     I still had very much faint hope that it only a version considered above the Non-standard situation....
>     Please, advise what to do!
>     After all even if though one calculation from my series will not turn out, all work will be gone...
>     I attach file REZULTAT.
>     Thanks in advance!
>

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          Tue Jan 12 '10 3:56pm
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