# CCL:G: Reaction path following with Gaussian

*From*: "A ron Vandeputte"
<Aaron.Vandeputte,Ugent.be>
*Subject*: CCL:G: Reaction path following with Gaussian
*Date*: Tue, 28 Mar 2006 02:35:34 -0500

Sent to CCL by: "A ron Vandeputte" [Aaron.Vandeputte ~~ Ugent.be]
In order to calculate tunneling corrections for H-abstractions, I'm trying to
calculate the Hessian along the reaction path of the H-abstraction CH3 + CH4
-> CH4 + CH3 with g03
However, if I use as input line
IRC(b3lyp/cbsb7,calcall,Cartesian,StepSize=1,MaxPoints=150,MaxCyc=50,verytight,forward)
int=ultrafine nosymm
calcultions fail to converge after 28 points. Gaussian iterates in cycles and
the same sequence of energies is calculated till the maximum number of steps is
exceeded.
If I use calcfc in stead of calcall, g03 has no trouble to converge but then I
don't get the wanted Hessian.
I would be very grateful if someone could help me with my problem.
Aron