TS search using lowest eigen value search

[Kbassyouni]

Hello, could someone please tell me the steps I need to do in order to perform a transition state search using the lowest eigen value search instead of calculating the complete hessian each time?
It is really important since my molecule is 142 atoms big.
Thanks in advance.

[christof.haettig]

Its described in the manual in the paragraphs "Finding Transition States" and "Keywords for Module aoforce".

[Kbassyouni]

Thank you but I have followed the manual step by step. I project the molecule in Tmolex then choose transition state seach then save it. Then I change the control file and insert $les all 1 and $h0hessian and $nomw, then I run on the cluster a jobex -trans job. It fails in the statpt step and says no initial hessian found.

[uwe]

Hello,

it is important to add

$les all 1

to the input before you start the frequency calculation, because this keyword is affecting only the hessian-generating step.

To search for a transition state using the lowest-eigenvalue search algorithm, just add

$les all 1
$statpt
  itrvec 1

to the control file and start

jobex -trans [..and other options if needed..]

The $nomw and $h0hessian keywords will automatically be added by the jobex script.

instead of calculating the complete hessian each time?

the hessian is not computed each time, it will be done (if no hessian can be found in the control file) only once at the beginning. Re-computing the hessian during the optimization is an optional feature which can be switched on by the hssfreq option in the $statpt section of your input.

Regards,

Uwe

[Kbassyouni]

Thank you.

regards,
Khaled