Re: CCL:gaussian03 optimization to transition state



 2004 July 2
 
People new to gaussian may wish to note that Gaussian *never* seems to find a transition state unless the NoEigentest (see below) keyword is included. I don't know why this is not the default. A good option is often Opt(TS, NoEigenTest, mndofc, MaxCycle=99).
 EL
 =====
 Yan Zhao wrote:
 
 Substitute "POpt=(Saddle=1)" for
 "opt=(ts,noeigentest,maxcycle=100)", then
 it will not stop because the wrong number of Negaative eigenvalues, if the
 optimization does not converge, you probably should try some better initial
 guesses of the geometry or add "calcfc" in the opt keyword.
 
Yan
 On 1 Jul 2004, Carsten Detering wrote:
 
 Hi all,
 
I would like to optimize a complex involving a bifurcated hydrogen bond between three nitrogen atoms (trimethylamine and triazen) to a saddle point (which I know exists from previous Mopac calculations). Taking this header line in the input file
 B3LYP/6-31g* POpt=(Saddle=1) nosymmetry test
 the optimization finishes with an error
 optimization stopped
 	--wrong number of Negative eigenvalues: Desired= 1 Actual= 2
 	--Flag reset to prevent archiving
 
Then I get, at the bottom, the typical proverb that you see only when a calculation has successfully finished, and then
 Could anybody make some suggestions how to fix this?
 Thanks a lot in advance,
 Carsten
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