Re: CCL:Locating a transition state

["Bin Shan" <philipbshan-0at0-hotmail.com>]

 Hi,
    Genzo,try something like this
 # opt(modredundant,TS,noeigen,CalcFC) rb3lyp/6-31g(d) nosymm
CalcFC calculates the initial force constants be computed at the first
 point
 and helps to determine which direction the atoms are to to move.The
 keyword
 noeigen and nosymm are also important.
   And it is also extremely important to specify a good initial
 guess.Finding transition state is by no means an easy task...according
 to my
 experience.
   Good luck.
 Bin
>  From: Genzo.Tanaka-0at0-netaspx.com
>  To: chemistry-0at0-ccl.net
>  Subject: CCL:Locating a transition state
>  Date: Fri, 26 Apr 2002 15:51:46 -0400
>  Hi,
>  I am trying to locate a transition state for a system about 30 atoms using
>  an empirical
>  method. So far I haven't had any success. I would appreciate if you could
>  give me any suggestions.
>  I am interested in a hydrolysis reaction pathway, using PM3 in Gaussian
>  98:
>  R-C-O-C-R' + H*-O'H ---> R-C-O-H*  + H-O'-C-R'
>  I have done the following:
>  1) opt=Ts ; This always failed due to incorrect number of negative
>  frequencies.
>  2) Scan  ; I have not tried much.
>  3) opt=ModRedundant: Scanning succeeded, but the population analysis after
>  the scanning seemed failed. The output did not indicate why it failed, but
>  the heading of population analysis appeared, followed by signal 11 error.
>  4) opt=qst2; There is (are) one or two statement(s) "stationary point was
>  found" (the distances were the same for all, but the angles and torsions
>  were slightly different in the two stationary points) in the output, but
>  the optimization (?) kept going and failed; Optimization aborted
>  --- No acceptable step or Inconsistency: ModMin=   2.
>  I optimized two reactant molecules individually and moved them close to
>  make
>  a reaction. The products were also optimized. The order of the atoms are
>  exactly the same.
>  Thanks,
>  Genzo Tanaka
>  Network Computing Services, Inc./
>  Army High Performance Computing Research Center at FAMU
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