I am performing an IRC calculation starting from the computed TS (one negative frequency). For the forward calculation, everything is OK. But for the reverse, the calculation stops at step 1, as energy increases, as if I was not starting from TS. Does someone have a suggestion?
Thank you
Dear Jerome,
If you start from the TS and you run a reaction coordinate for a bond X-Y, you should divide your calculations into two parts:
(1) Part 1; You increase the X-Y bond in increment of 0.1 or 0.05 Angstrom
(2) Part 2; You decrease the X-Y bond in increment of 0.1 or 0.05 Angstrom
If you are doing for angle A-B-C; you should follow the same as for the bond.
Using this strategy you will avoid any unexpected results.
I think what happened in your calculations is that you reached an imaginary structure (fault structure) with a high energy which results in stopping the calculations.
Hoping this will be helpful,
Rafik
Dear Rafik
Many thanks for the kind answer. I think I had more or less followed your procedure. My step size is 10, therefore, corresponding to 0.05 Angstrom (for a bond X-Y). I will reduce the step to 5, to see if it improves (it will cost more computing time!).
Thanks
Jerome
Dear Oleg, thank you very much for the help. Indeed this is helpful. I have started to do what Rafik suggested above, that is to say decrease the step size (to 5)...I have also asked the computer to calculate frequencies at all steps (calcall). So far it seems to work...but it is very slow due to the frequency calculation. Wait and see...
Thank you for your help
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