CCL:G: gaussian 09: difficulties with IRC

 Sent to CCL by: "Inbal Tuvi-Arad" [inbaltu,,openu.ac.il]
 Dear Pierre,
  Perhaps reducing the step size to 7, 5, and even less will help.
 Best wishes,
 Inbal
 -----Original Message-----
 > From: owner-chemistry+inbaltu==openu.ac.il*_*ccl.net
 [mailto:owner-chemistry+inbaltu==openu.ac.il*_*ccl.net] On
 Behalf Of
 Pierre Archirel pierre.archirel||u-psud.fr
 Sent: Monday, February 15, 2010 5:22 PM
 To: Inbal Tuvi-Arad
 Subject: CCL:G: gaussian 09: difficulties with IRC
 Sent to CCL by: "Pierre  Archirel" [pierre.archirel^u-psud.fr]
 Dear colleagues,
 I have localised a TS for a probably floppy molecule (a seven membered
 ring),
 I now wish to follow down the reaction path to the potential wells.
 The question is that gaussian 09 simply cannot depart, probably because
 the barrier top is too flat. How can I fix this issue? Thanks in
 advance.
 These is my data line:
  irc=(forward,calcfc,hpc,maxpoints=200,maxcycle=50,stepsize=10,tight)
 I have varied two options: stepsize=10, 20 and 50 and ordinary, tight
 and vtight accuracy, and combinations of them. This is a typical output:
 IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC
  Error in corrector energy =           0.0000000087
  Magnitude of corrector gradient =     0.0000440598
  Magnitude of analytic gradient =      0.0000465467
  Magnitude of difference =             0.0000332442
  Angle between gradients (degrees)=   42.9405
  Pt  1 Step number  20 out of a maximum of  50
  CORRECTOR INTEGRATION CONVERGENCE:
    Recorrection delta-x convergence threshold:    0.001826
    Delta-x Convergence Met
  Point Number:   1          Path Number:   1
    CHANGE IN THE REACTION COORDINATE =    0.00327
    NET REACTION COORDINATE UP TO THIS POINT =    0.00327
   # OF POINTS ALONG THE PATH =   1
   # OF STEPS =  20
  PES minimum detected on this side of the pathway.
     Magnitude of the gradient =      0.0000441
  Calculation of FORWARD path complete.
  Reaction path calculation complete.
  Energies reported relative to the TS energy of        -204.117456
 ------------------------------------------------------------------------
 --
     Summary of reaction path following
 ------------------------------------------------------------------------
 --
                         Energy   Rx Coord
    1                    0.00000   0.00000
    2                    0.00000   0.00327
 ------------------------------------------------------------------------
 --
  Total number of points:                    1
  Total number of gradient calculations:    21
  Total number of Hessian calculations:      1
  IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC
 Pierre Archirel
 pierre.archirel||u-psud.fr
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