[molpro-user] Problem regarding IRC with method QSDPATH
gmahesh at students.iiserpune.ac.in
Fri Aug 23 07:29:26 BST 2013
I thought, the problem arising in IRC was because of negative Hessian
eigenvalues but, now I realized that's not the case. Earlier I have done
transition state optimization with Hessian calculated by forward
differences and IRC with central differences so that, it was giving 4
negative Hessian values in the case of IRC.
Now I ran IRC with calculating Hessian using forward differences and all
positive Hessian eigenvalues except one got too. Even now also surprisingly
giving the same error which I got earlier. Here, I also have posted the
echo of output having error.
***********Partial out put************
Geometry optimization using default procedure for command MULTI
Geometry written to block 1 of record 700
Generated 9 symmetrical displacements
Numerically approximating hessian using forward gradient differences
Task list generated. Total number of displacements: 9
5 tasks completed, CPU=1h 3m 15s Elapsed=1h 10m 13s
Numerical MULTI000 hessian completed. CPU-time: 6877.21 sec, Elapsed:
MULTI hessian saved to record 5300.2
Quadratic Steepest Descent - Reaction Path Following using exact Hessian
Hessian eigenvalues: -0.012734 0.000786 0.011948 0.018747 0.075415
0.141616 0.303108 1.646533 1.810536
IDIR= 1 requested but starting point is not a stationary point. Gradient
norm= 0.98D-04 Step length= 0.36D-01
? Not a stationary point
? The problem occurs in QSDPATH1
What's wrong I am doing here....??
On Wed, Aug 21, 2013 at 9:18 PM, Ramon Hernandez <ramon at uaem.mx> wrote:
> Dear Mahi,
> I suggest you double-check that indeed your initial CASSCF calculation
> to a transition state, perhaps run a frequency calculation with tight
> parameters. Then
> when you run the IRC make sure you indeed converge to the same energy
> as the original
> CASSCF calculation. If you are sure about both these points then the
> problem might really
> have to do with a bug in IRC.
> Also if you run again the initial frequency calculation you can save
> that information and
> then read it directly in the next IRC job so you avoid calculating it
> 2013/8/21, G Mahesh <gmahesh at students.iiserpune.ac.in>:
> > 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
> > frequency (150 cm-1) and this normal mode having imaginary frequency
> > like reaction mode which will connect reactants to products.
> > Now the problem is with IRC, here, I started IRC with the geometry which
> > got from the transition state optimization with QSDPATH method and IDIR=1
> > then, after Hessian calculation, it's complaining that, the given
> > is not stationary with 4 negative Hessian eigenvalues. Does this means,
> > 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.
> > Thanks,
> > Mahi
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