mess.inp example: TS Frequencies and .dat file

[mtm60]

Hello, I was wondering if I could get some more detail on the mess.inp example. I was primarily wondering about the lack of a negative vibrational frequency in the barrier section, in addition to the contents of the .dat file provided. Is this barrier not a transition state? What does the .dat file include?

Thank you!

[ygeorgi]

Hi,
Sorry for the late reply. Apparently i have missed the related email and suddenly bumped into it.

Concerning the negative (imaginary) frequency: it is included into the tunneling subsection, if it is available. Otherwise, imaginary frequency does not effect the barrier number of states.

About the .dat file i am not sure. What it is related to?
Thanks,
Yuri

[avcopan]

@ygeorgi I believe @mtm60 is referring to this file that gets imported in our example input file here.

[ygeorgi]

I see ... Ok, this file provides the variationally optimized number of states for transitional (rotational + translational) degrees of freedom, which is obtained by other means (rotd / VaReCoF). The reason is that for barrier-less processes the transition state is loose and the RRHO model is not applicable. The transitional modes number of states is calculated by direct sampling. The simple alternative is Phase Space Theory.