I began running IRC calculations from the optimized TS. Before starting irc I did frequency calculation which confirm that my Ts is stationary point and the first frequency is negative. But IRC calculations did one step and it was said that "PES minimum detected on this side of the pathway." Then I took the structure from IRC calculations, run frequency calculations and start IRC again. It did only one step again. I have Ts between CTC and TTC forms. I've attached the log file of IRC calculations below.
Thank you in advance!
Could you please, provide us with TS structure...so that, one can find out the reason behind this.....
Dear Olga,
While I need your optimized TS structure, it seems your try corresponds to find the TS of a cis-trans isomerization. An initial assessment of your IRC indicates that your located TS should not be a true and valid first-order saddle point (while you may get an imaginary frequency). Note that such an isomerization cannot take place via a one-step mechanism. Indeed, the C=C double bond should firstly break via various mechanisms which can be feasible in the reaction mixture and, then, generated C-C single bond is allowed to be rotated. Please let me to know a detailed information about the reaction you are working on.
P.S
Tomorrow, I will be out of city and your reply will be considered Friday.
Regards,
Saeed
Thank you four your answers!
Here I attached optimized structures of my CTC snd TTC structures and optimized TS.
If you are using gaussian09, that is a common problem. The easiest solution is to use the option 'calcall' in IRC step rather than using 'readfc'. The following keyword in your input should resolve the problem:
irc(report=cartesians,forward,calcall,maxpoints=200,stepsize=2,maxcycle=512)
please don forget to supply the optimized TS geometry in the input section (rather than guessing it from checkpoint).
Dear Manoj Kumar, I run calculations with calcall, but unfortunatelly it did only one step again.
I've tried calcall and with different values of stepsize and maxpoints but gaussian did only one step again. Do you have any ideas why?
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