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Re: how to exclude certain frequencies

Alex Granovsky
gran@classic.chem.msu.su


Hi,

there is no way how to do that. While you can recount thermodynamic
functions manually after having obtaining frequencies, I'd not recommend
doing so. Indeed, the mode with small imaginary frequency requires
a separate investigation. It is quite possibly that it is actually
a (real) low-frequency vibration and so its contribution to thermodynamic
functions cannot be neglected. What I would suggest is to perform
hessian calculation increasing their overall precision (i.e. using
tightened ICUT, nconv, set nvib=2 etc... etc...)

Kind regards,
Alex Granovsky


On Tue Feb 21 '12 9:01am, Eldar Mamin wrote
-------------------------------------------
>Dear Dr. Granovsky, developers and users of FireFly,
>
>Can you help me how to exclude certain frequencies  from
>nornal mode analysis in FF job.
>PLEASE VERIFY THE PROGRAM'S DECISION MANUALLY! - said the
>programm, but
>nothing more to DO this. I see one imaginagy frequency of
>rotation of whole system after a frequency of reaction motion. But programm excluded both 2
>imaginary ones and so
>following six frequencies too taking them as a rot and trans, but one of these six is a
>vibration, so i got
>erroneous entropy, enthalpy etc.
>Hope you help, Eldar Mamin.


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