Subject: about precomplex

From: Yunfeng Hu <[email-masked]>
Date: Wed, 10 Nov 1999 13:44:19 -0800 (PST)

Hi,everyone
Recently I'm doing some ion reaction and dipolar cycloaddition
calculation. I found in both cases that the energy of reactants(simple 
energy sum of each reactant faraway) is larger than that of TS in gas
phase. Can someone tell me how to find the precomplex in an unexpensive
way? 
Thanks in advance.

Yunfeng

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From: David Gallagher <[email-masked]>
Date: Wed, 10 Nov 1999 15:18:35 -0800

If you are using MOPAC, first check you have a true transition state by
running a FORCE calculation which should show one and only one negative
vibration. Then run the IRC=1 and IRC=-1 calculations to find the reactants
and products (minima) on either side of the transition state. One of these
may lead to the precomplex or intermediate that you suspect.

Regards,

David Gallagher, Fujitsu CCS.