[molpro-user] Problem regarding IRC with method QSDPATH

G Mahesh gmahesh at students.iiserpune.ac.in
Wed Aug 21 06:11:38 BST 2013

Dear all,

I am familiar with MOLPRO from last two months. Since then I am trying to
find a transition state for the reaction of reactants and products having
multi reference character so, I am using CASSCF method for my problem.
After a long struggle, I have found the transition state with one imaginary
frequency (150 cm-1) and this normal mode having imaginary frequency seems
like reaction mode which will connect reactants to products.

Now the problem is with IRC, here, I started IRC with the geometry which I
got from the transition state optimization with QSDPATH method and IDIR=1
then, after Hessian calculation, it's complaining that, the given structure
is not stationary with 4 negative Hessian eigenvalues. Does this means, my
initial structure is not real transition state structure.....??  Should I
have to try for the transition state structure again ..?? Any ideas to
solve the problem....?? Pls help me...!

Below additional details may be required to understand the problem.

We are using the MOLPRO version 2012.
Our system has 5 atoms. We are using 13 active orbitals and 15 active
electrons as my cas space and AVTZ as basis.

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