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Re^5: $IRC keyword definition

Leira Ruth A. F.
leiraruth@gmail.com


Dear Sir,

Thank you for making things clear. I just noticed that even if I get either of the reactant or product structures as end geometries of my forwrd=.t. and forwrd=.f. calculations, their energies did not match to those in my optimization calculations. I also tried running an optimization to those geometries I obtained from IRC but still did not match to the ones in the former optimization calculation. The difference I get is about 0.54 Hartrees and I'm using B3LYP/6-31Gd level of theory. Aren't they supposed to be almost the same (about 1E-6 difference) in their total energies?

Hoping to hear from you soon,
Leira

On Thu Jun 6 '13 2:32pm, Luca Maidich wrote
-------------------------------------------
>Dear Leira,
>I'm glad to know that the post helped you and thanks for letting me know it :)
>I can tell you that I used the same input file just changing the value of FORWRD (.T. or .F.) so, basically, yes I used the same $DATA and $HESS deck. The coordinates in $DATA are those of the saddle point (I got them directly from the hessian job) and the $HESS group has been copied as it appears in the PUNCH file.

>If I understood correctly how Firefly works, there is no need to apply a distortion to the geometry in the desired direction (I think it can be difficult sometimes but trivial in some others) because when you set FORWRD=.T. or FORWRD=.F. you are telling the program to follow the imaginary mode in the positive or negative direction. Please be aware that positive doesn't mean necessarily products.

>Hope this helps,
>Kind Regards
>Luca


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