[molpro-user] Starting point is not a critical point

[Gabriel Freitas]

Dear professor Werner and colleagues,

I see the point, but it's not the case.

I have converged the geometry and calculated the frequencies both using
symmetry (in which I froze the dihedral coordinate - my molecule has 4
atoms, and this particular isomer is planar) or not, and normal modes
confirm that I have a TS (no warning message regarding gradient
norms). It's true that when it's optimized without symmetry, the dihedral
plane is not exactly zero (the value when symmetry is on), but it's lower
than 1 degree, and frequencies are essentially the same.

Regards,

Gabriel



2012/1/9 Hans-Joachim Werner <werner at theochem.uni-stuttgart.de>

> This can happen if you optimize the transition state in a limited
> parameter space.
> The IRC optimization requires a full optimization (3N-6 coordinates).
> Please check
> if that is the case!
> Best regards
> Joachim Werner
> Am 08.01.2012 um 16:30 schrieb Gabriel Freitas:
>
> Dear molpro users/developers,
>
> I'm trying to do an IRC calculation from a transition state previously
> calculated. But by the time the qsdpath takes its first step, I get the
> message:
>
> *QSDPATH2: Starting point is not a critical point.*
>
> I've tried many things, but unsuccessfully, and I'm afraid there can be a
> bug in the code.
>
> Here follows one example, in which I reoptmize the TS (which converges in
> a single step, since the starting geometry is already converged) and ask
> for IRC using the hessian calculated during the TS search.
>
>
> Part of the input
>
> XXXXXXXXXXXX
>  nosym
>  R1=1.34210982 ang,
>  R2=1.76235720 ang,
>  R3=1.30142476 ang,
>  a=92.77261716 degree,
>  b=113.97606866 degree,
>  g=0.00000 degree
>  geometry={ }
>  rhf,maxdis=50,maxit=100;
>  rccsd(t),maxit=70;
>  {optg,root=2,method=qsd,maxit=100,saveact=...,rewind;print,history}
>
>  {optg,method=qsdpath,hessrec=5300.2,dir=+3,numhess=0,hesscentral,maxit=100;print,history}
>
> XXXXXXXXXXXXXXX
>
> *Part of the output*
>
> XXXXXXXXX
>
>  PROGRAM * OPT (Geometry optimization)     Authors: F. Eckert and H.-J.
> Werner
>
>  Geometry optimization using default procedure for command RCCSD(T)
>
>  Numerically approximating hessian using central energy differences
>
>  Task list generated. Total number of displacements:     42
>
>  ....
>
>  Numerical RCCSD(T) hessian completed. CPU-time: 31364.93 sec, Elapsed:
> 33653.29 sec
>
>  RCCSD(T) hessian saved to record  5300.2
>
>  Combined Powell-Murtagh-Sargent Update of Hessian
>
>  Quadratic Steepest Descent -  Transition State Search
>
>  Optimization point 1
>
>  Variable                      Last           Current        Next
>   Gradient       Hessian
>
>  E(RCCSD(T)) / Hartree       0.00000000  -548.43957924     0.00000000
>  R1 / ANG                    0.00000000     1.34210982     1.34215444
>  -0.00004976     0.97545936
>  R2 / ANG                    0.00000000     1.76235720     1.76307008
>  -0.00025977     0.46872502
>  A / DEGREE                  0.00000000    92.77261716    92.75401930
> 0.00000022     0.00006113
>  R3 / ANG                    0.00000000     1.30142476     1.30118943
> 0.00017736     1.53165483
>   B / DEGREE                  0.00000000   113.97606866   113.97094779
> 0.00000020     0.00009433
>  G / DEGREE                  0.00000000     0.00000000    -0.06878260
> 0.00000000     0.00000090
>  Convergence:                0.00000000  (line search)     0.00189055
> 0.00016936  (total)
>
>  END OF GEOMETRY OPTIMIZATION.    TOTAL CPU:     31240.2 SEC
>
>
>  PROGRAM * OPT (Geometry optimization)     Authors: F. Eckert and H.-J.
> Werner
>
>
>  Geometry optimization using default procedure for command RCCSD(T)
>
>
>  Number of displacements for numerical gradient:     12
>
>  Starting numerical gradient for RCCSD(T)
>
>  Numerical gradient completed. CPU-time:  8776.29 sec, Elapsed:  9365.30
> sec
>
>  RCCSD(T) hessian read from record  5300.2
>
>  Combined Powell-Murtagh-Sargent Update of Hessian
>
>  Quadratic Steepest Descent -  Reaction Path Following using updated
> Hessian
>
>  Hessian eigenvalues:     0.002870  0.102644  0.198864  0.270747  0.292713
>  0.478791
>
>  QSDPATH2: Starting point is not a critical point.
>  Performing a regular QSD step. Stepsize =  0.075068    Curvature =
> .49831D+04
>
>  Optimization point 1
>
>  Variable                      Last           Current        Next
>   Gradient       Hessian
>
>  E(RCCSD(T)) / Hartree       0.00000000  -548.43957912     0.00000000
>  R1 / ANG                    0.00000000     1.34215444     1.34215192
>  -0.00000415     0.97545936
>  R2 / ANG                    0.00000000     1.76307008     1.76311166
>  -0.00002081     0.46872502
>  A / DEGREE                  0.00000000    92.75401930    92.75259887
> 0.00000000     0.00006113
>   R3 / ANG                    0.00000000     1.30118943     1.30117610
> 0.00000355     1.53165483
>  B / DEGREE                  0.00000000   113.97094779   113.97050327
>  -0.00000001     0.00009433
>  G / DEGREE                  0.00000000    -0.06878260    -0.14458311
> 0.00000007     0.00000090
>  Convergence:                1.00000000  (line search)     0.00132580
> 0.00001209  (total)
>
> XXXXX
>
> Although the hessian is calculated for a geometry slightly displaced from
> the one used for the gradient calculation, it can be seen that both
> gradients are smaller than the default converge threshold,
>
> Any help would be very appreciated.
>
> Regards,
>
> --
> Gabriel do Nascimento Freitas
> D.Sc. Student - Graduate Program of Chemistry
> Molecular Modelling and Theoretical Chemistry Laboratory - Room 412
> Chemistry Institute - Universidade Federal do Rio de Janeiro (UFRJ) -
> Brazil
> (+5521)8830-9971 / (+5521)2562-7179
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>
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